email policy works mm

12 files changed, 5868 insertions, 5 deletions

diff --git a/modules/language/python/module/email/_encoded_words.py b/modules/language/python/module/email/_encoded_words.py
new file mode 100644
index 0000000..8c02709
--- /dev/null
+++ b/modules/language/python/module/email/_encoded_words.py
@@ -0,0 +1,222 @@
+module(email,_encoded_words)
+""" Routines for manipulating RFC2047 encoded words.
+
+This is currently a package-private API, but will be considered for promotion
+to a public API if there is demand.
+
+"""
+
+# An ecoded word looks like this:
+#
+#        =?charset[*lang]?cte?encoded_string?=
+#
+# for more information about charset see the charset module.  Here it is one
+# of the preferred MIME charset names (hopefully; you never know when parsing).
+# cte (Content Transfer Encoding) is either 'q' or 'b' (ignoring case).  In
+# theory other letters could be used for other encodings, but in practice this
+# (almost?) never happens.  There could be a public API for adding entries
+# to the CTE tables, but YAGNI for now.  'q' is Quoted Printable, 'b' is
+# Base64.  The meaning of encoded_string should be obvious.  'lang' is optional
+# as indicated by the brackets (they are not part of the syntax) but is almost
+# never encountered in practice.
+#
+# The general interface for a CTE decoder is that it takes the encoded_string
+# as its argument, and returns a tuple (cte_decoded_string, defects).  The
+# cte_decoded_string is the original binary that was encoded using the
+# specified cte.  'defects' is a list of MessageDefect instances indicating any
+# problems encountered during conversion.  'charset' and 'lang' are the
+# corresponding strings extracted from the EW, case preserved.
+#
+# The general interface for a CTE encoder is that it takes a binary sequence
+# as input and returns the cte_encoded_string, which is an ascii-only string.
+#
+# Each decoder must also supply a length function that takes the binary
+# sequence as its argument and returns the length of the resulting encoded
+# string.
+#
+# The main API functions for the module are decode, which calls the decoder
+# referenced by the cte specifier, and encode, which adds the appropriate
+# RFC 2047 "chrome" to the encoded string, and can optionally automatically
+# select the shortest possible encoding.  See their docstrings below for
+# details.
+
+import re
+import base64
+import binascii
+import functools
+from string import ascii_letters, digits
+import email.errors as errors
+
+__all__ = ['decode_q',
+           'encode_q',
+           'decode_b',
+           'encode_b',
+           'len_q',
+           'len_b',
+           'decode',
+           'encode',
+           ]
+
+#
+# Quoted Printable
+#
+
+# regex based decoder.
+_q_byte_subber = functools.partial(re.compile(br'=([a-fA-F0-9]{2})').sub,
+        lambda m: bytes([int(m.group(1), 16)]))
+
+def decode_q(encoded):
+    encoded = encoded.replace(b'_', b' ')
+    return _q_byte_subber(encoded), []
+
+
+# dict mapping bytes to their encoded form
+class _QByteMap(dict):
+
+    safe = b'-!*+/' + ascii_letters.encode('ascii') + digits.encode('ascii')
+
+    def __missing__(self, key):
+        if key in self.safe:
+            self[key] = chr(key)
+        else:
+            self[key] = "={:02X}".format(key)
+        return self[key]
+
+_q_byte_map = _QByteMap()
+
+# In headers spaces are mapped to '_'.
+_q_byte_map[ord(' ')] = '_'
+
+def encode_q(bstring):
+    return ''.join(_q_byte_map[x] for x in bstring)
+
+def len_q(bstring):
+    return sum(len(_q_byte_map[x]) for x in bstring)
+
+
+#
+# Base64
+#
+
+def decode_b(encoded):
+    defects = []
+    pad_err = len(encoded) % 4
+    if pad_err:
+        defects.append(errors.InvalidBase64PaddingDefect())
+        padded_encoded = encoded + b'==='[:4-pad_err]
+    else:
+        padded_encoded = encoded
+    try:
+        return base64.b64decode(padded_encoded, validate=True), defects
+    except binascii.Error:
+        # Since we had correct padding, this must an invalid char error.
+        defects = [errors.InvalidBase64CharactersDefect()]
+        # The non-alphabet characters are ignored as far as padding
+        # goes, but we don't know how many there are.  So we'll just
+        # try various padding lengths until something works.
+        for i in 0, 1, 2, 3:
+            try:
+                return base64.b64decode(encoded+b'='*i, validate=False), defects
+            except binascii.Error:
+                if i==0:
+                    defects.append(errors.InvalidBase64PaddingDefect())
+        else:
+            # This should never happen.
+            raise AssertionError("unexpected binascii.Error")
+
+def encode_b(bstring):
+    return base64.b64encode(bstring).decode('ascii')
+
+def len_b(bstring):
+    groups_of_3, leftover = divmod(len(bstring), 3)
+    # 4 bytes out for each 3 bytes (or nonzero fraction thereof) in.
+    return groups_of_3 * 4 + (4 if leftover else 0)
+
+
+_cte_decoders = {
+    'q': decode_q,
+    'b': decode_b,
+    }
+
+def decode(ew):
+    """Decode encoded word and return (string, charset, lang, defects) tuple.
+
+    An RFC 2047/2243 encoded word has the form:
+
+        =?charset*lang?cte?encoded_string?=
+
+    where '*lang' may be omitted but the other parts may not be.
+
+    This function expects exactly such a string (that is, it does not check the
+    syntax and may raise errors if the string is not well formed), and returns
+    the encoded_string decoded first from its Content Transfer Encoding and
+    then from the resulting bytes into unicode using the specified charset.  If
+    the cte-decoded string does not successfully decode using the specified
+    character set, a defect is added to the defects list and the unknown octets
+    are replaced by the unicode 'unknown' character \\uFDFF.
+
+    The specified charset and language are returned.  The default for language,
+    which is rarely if ever encountered, is the empty string.
+
+    """
+    _, charset, cte, cte_string, _ = ew.split('?')
+    charset, _, lang = charset.partition('*')
+    cte = cte.lower()
+    # Recover the original bytes and do CTE decoding.
+    bstring = cte_string.encode('ascii', 'surrogateescape')
+    bstring, defects = _cte_decoders[cte](bstring)
+    # Turn the CTE decoded bytes into unicode.
+    try:
+        string = bstring.decode(charset)
+    except UnicodeError:
+        defects.append(errors.UndecodableBytesDefect("Encoded word "
+            "contains bytes not decodable using {} charset".format(charset)))
+        string = bstring.decode(charset, 'surrogateescape')
+    except LookupError:
+        string = bstring.decode('ascii', 'surrogateescape')
+        if charset.lower() != 'unknown-8bit':
+            defects.append(errors.CharsetError("Unknown charset {} "
+                "in encoded word; decoded as unknown bytes".format(charset)))
+    return string, charset, lang, defects
+
+
+_cte_encoders = {
+    'q': encode_q,
+    'b': encode_b,
+    }
+
+_cte_encode_length = {
+    'q': len_q,
+    'b': len_b,
+    }
+
+def encode(string, charset='utf-8', encoding=None, lang=''):
+    """Encode string using the CTE encoding that produces the shorter result.
+
+    Produces an RFC 2047/2243 encoded word of the form:
+
+        =?charset*lang?cte?encoded_string?=
+
+    where '*lang' is omitted unless the 'lang' parameter is given a value.
+    Optional argument charset (defaults to utf-8) specifies the charset to use
+    to encode the string to binary before CTE encoding it.  Optional argument
+    'encoding' is the cte specifier for the encoding that should be used ('q'
+    or 'b'); if it is None (the default) the encoding which produces the
+    shortest encoded sequence is used, except that 'q' is preferred if it is up
+    to five characters longer.  Optional argument 'lang' (default '') gives the
+    RFC 2243 language string to specify in the encoded word.
+
+    """
+    if charset == 'unknown-8bit':
+        bstring = string.encode('ascii', 'surrogateescape')
+    else:
+        bstring = string.encode(charset)
+    if encoding is None:
+        qlen = _cte_encode_length['q'](bstring)
+        blen = _cte_encode_length['b'](bstring)
+        # Bias toward q.  5 is arbitrary.
+        encoding = 'q' if qlen - blen < 5 else 'b'
+    encoded = _cte_encoders[encoding](bstring)
+    if lang:
+        lang = '*' + lang
+    return "=?{}{}?{}?{}?=".format(charset, lang, encoding, encoded)
diff --git a/modules/language/python/module/email/_header_value_parser.py b/modules/language/python/module/email/_header_value_parser.py
new file mode 100644
index 0000000..0f4a1cb
--- /dev/null
+++ b/modules/language/python/module/email/_header_value_parser.py
@@ -0,0 +1,2820 @@
+module(email,_header_value_parser)
+
+"""Header value parser implementing various email-related RFC parsing rules.
+
+The parsing methods defined in this module implement various email related
+parsing rules.  Principal among them is RFC 5322, which is the followon
+to RFC 2822 and primarily a clarification of the former.  It also implements
+RFC 2047 encoded word decoding.
+
+RFC 5322 goes to considerable trouble to maintain backward compatibility with
+RFC 822 in the parse phase, while cleaning up the structure on the generation
+phase.  This parser supports correct RFC 5322 generation by tagging white space
+as folding white space only when folding is allowed in the non-obsolete rule
+sets.  Actually, the parser is even more generous when accepting input than RFC
+5322 mandates, following the spirit of Postel's Law, which RFC 5322 encourages.
+Where possible deviations from the standard are annotated on the 'defects'
+attribute of tokens that deviate.
+
+The general structure of the parser follows RFC 5322, and uses its terminology
+where there is a direct correspondence.  Where the implementation requires a
+somewhat different structure than that used by the formal grammar, new terms
+that mimic the closest existing terms are used.  Thus, it really helps to have
+a copy of RFC 5322 handy when studying this code.
+
+Input to the parser is a string that has already been unfolded according to
+RFC 5322 rules.  According to the RFC this unfolding is the very first step, and
+this parser leaves the unfolding step to a higher level message parser, which
+will have already detected the line breaks that need unfolding while
+determining the beginning and end of each header.
+
+The output of the parser is a TokenList object, which is a list subclass.  A
+TokenList is a recursive data structure.  The terminal nodes of the structure
+are Terminal objects, which are subclasses of str.  These do not correspond
+directly to terminal objects in the formal grammar, but are instead more
+practical higher level combinations of true terminals.
+
+All TokenList and Terminal objects have a 'value' attribute, which produces the
+semantically meaningful value of that part of the parse subtree.  The value of
+all whitespace tokens (no matter how many sub-tokens they may contain) is a
+single space, as per the RFC rules.  This includes 'CFWS', which is herein
+included in the general class of whitespace tokens.  There is one exception to
+the rule that whitespace tokens are collapsed into single spaces in values: in
+the value of a 'bare-quoted-string' (a quoted-string with no leading or
+trailing whitespace), any whitespace that appeared between the quotation marks
+is preserved in the returned value.  Note that in all Terminal strings quoted
+pairs are turned into their unquoted values.
+
+All TokenList and Terminal objects also have a string value, which attempts to
+be a "canonical" representation of the RFC-compliant form of the substring that
+produced the parsed subtree, including minimal use of quoted pair quoting.
+Whitespace runs are not collapsed.
+
+Comment tokens also have a 'content' attribute providing the string found
+between the parens (including any nested comments) with whitespace preserved.
+
+All TokenList and Terminal objects have a 'defects' attribute which is a
+possibly empty list all of the defects found while creating the token.  Defects
+may appear on any token in the tree, and a composite list of all defects in the
+subtree is available through the 'all_defects' attribute of any node.  (For
+Terminal notes x.defects == x.all_defects.)
+
+Each object in a parse tree is called a 'token', and each has a 'token_type'
+attribute that gives the name from the RFC 5322 grammar that it represents.
+Not all RFC 5322 nodes are produced, and there is one non-RFC 5322 node that
+may be produced: 'ptext'.  A 'ptext' is a string of printable ascii characters.
+It is returned in place of lists of (ctext/quoted-pair) and
+(qtext/quoted-pair).
+
+XXX: provide complete list of token types.
+"""
+
+import re
+import urllib.parse as parse   # For urllib.parse.unquote
+from string import hexdigits
+from collections import OrderedDict
+from operator import itemgetter
+import email._encoded_words as _ew
+import email.errors as errors
+import email.utils as utils
+
+#
+# Useful constants and functions
+#
+
+WSP = set(' \t')
+CFWS_LEADER = WSP | set('(')
+SPECIALS = set(r'()<>@,:;.\"[]')
+ATOM_ENDS = SPECIALS | WSP
+DOT_ATOM_ENDS = ATOM_ENDS - set('.')
+# '.', '"', and '(' do not end phrases in order to support obs-phrase
+PHRASE_ENDS = SPECIALS - set('."(')
+TSPECIALS = (SPECIALS | set('/?=')) - set('.')
+TOKEN_ENDS = TSPECIALS | WSP
+ASPECIALS = TSPECIALS | set("*'%")
+ATTRIBUTE_ENDS = ASPECIALS | WSP
+EXTENDED_ATTRIBUTE_ENDS = ATTRIBUTE_ENDS - set('%')
+
+def quote_string(value):
+    return '"'+str(value).replace('\\', '\\\\').replace('"', r'\"')+'"'
+
+#
+# TokenList and its subclasses
+#
+
+class TokenList(list):
+
+    token_type = None
+    syntactic_break = True
+    ew_combine_allowed = True
+
+    def __init__(self, *args, **kw):
+        super().__init__(*args, **kw)
+        self.defects = []
+
+    def __str__(self):
+        return ''.join(str(x) for x in self)
+
+    def __repr__(self):
+        return '{}({})'.format(self.__class__.__name__,
+                             super().__repr__())
+
+    @property
+    def value(self):
+        return ''.join(x.value for x in self if x.value)
+
+    @property
+    def all_defects(self):
+        return sum((x.all_defects for x in self), self.defects)
+
+    def startswith_fws(self):
+        return self[0].startswith_fws()
+
+    @property
+    def as_ew_allowed(self):
+        """True if all top level tokens of this part may be RFC2047 encoded."""
+        return all(part.as_ew_allowed for part in self)
+
+    @property
+    def comments(self):
+        comments = []
+        for token in self:
+            comments.extend(token.comments)
+        return comments
+
+    def fold(self, *, policy):
+        return _refold_parse_tree(self, policy=policy)
+
+    def pprint(self, indent=''):
+        print(self.ppstr(indent=indent))
+
+    def ppstr(self, indent=''):
+        return '\n'.join(self._pp(indent=indent))
+
+    def _pp(self, indent=''):
+        yield '{}{}/{}('.format(
+            indent,
+            self.__class__.__name__,
+            self.token_type)
+        for token in self:
+            if not hasattr(token, '_pp'):
+                yield (indent + '    !! invalid element in token '
+                                        'list: {!r}'.format(token))
+            else:
+                yield from token._pp(indent+'    ')
+        if self.defects:
+            extra = ' Defects: {}'.format(self.defects)
+        else:
+            extra = ''
+        yield '{}){}'.format(indent, extra)
+
+
+class WhiteSpaceTokenList(TokenList):
+
+    @property
+    def value(self):
+        return ' '
+
+    @property
+    def comments(self):
+        return [x.content for x in self if x.token_type=='comment']
+
+
+class UnstructuredTokenList(TokenList):
+
+    token_type = 'unstructured'
+
+
+class Phrase(TokenList):
+
+    token_type = 'phrase'
+
+class Word(TokenList):
+
+    token_type = 'word'
+
+
+class CFWSList(WhiteSpaceTokenList):
+
+    token_type = 'cfws'
+
+
+class Atom(TokenList):
+
+    token_type = 'atom'
+
+
+class Token(TokenList):
+
+    token_type = 'token'
+    encode_as_ew = False
+
+
+class EncodedWord(TokenList):
+
+    token_type = 'encoded-word'
+    cte = None
+    charset = None
+    lang = None
+
+
+class QuotedString(TokenList):
+
+    token_type = 'quoted-string'
+
+    @property
+    def content(self):
+        for x in self:
+            if x.token_type == 'bare-quoted-string':
+                return x.value
+
+    @property
+    def quoted_value(self):
+        res = []
+        for x in self:
+            if x.token_type == 'bare-quoted-string':
+                res.append(str(x))
+            else:
+                res.append(x.value)
+        return ''.join(res)
+
+    @property
+    def stripped_value(self):
+        for token in self:
+            if token.token_type == 'bare-quoted-string':
+                return token.value
+
+
+class BareQuotedString(QuotedString):
+
+    token_type = 'bare-quoted-string'
+
+    def __str__(self):
+        return quote_string(''.join(str(x) for x in self))
+
+    @property
+    def value(self):
+        return ''.join(str(x) for x in self)
+
+
+class Comment(WhiteSpaceTokenList):
+
+    token_type = 'comment'
+
+    def __str__(self):
+        return ''.join(sum([
+                            ["("],
+                            [self.quote(x) for x in self],
+                            [")"],
+                            ], []))
+
+    def quote(self, value):
+        if value.token_type == 'comment':
+            return str(value)
+        return str(value).replace('\\', '\\\\').replace(
+                                  '(', r'\(').replace(
+                                  ')', r'\)')
+
+    @property
+    def content(self):
+        return ''.join(str(x) for x in self)
+
+    @property
+    def comments(self):
+        return [self.content]
+
+class AddressList(TokenList):
+
+    token_type = 'address-list'
+
+    @property
+    def addresses(self):
+        return [x for x in self if x.token_type=='address']
+
+    @property
+    def mailboxes(self):
+        return sum((x.mailboxes
+                    for x in self if x.token_type=='address'), [])
+
+    @property
+    def all_mailboxes(self):
+        return sum((x.all_mailboxes
+                    for x in self if x.token_type=='address'), [])
+
+
+class Address(TokenList):
+
+    token_type = 'address'
+
+    @property
+    def display_name(self):
+        if self[0].token_type == 'group':
+            return self[0].display_name
+
+    @property
+    def mailboxes(self):
+        if self[0].token_type == 'mailbox':
+            return [self[0]]
+        elif self[0].token_type == 'invalid-mailbox':
+            return []
+        return self[0].mailboxes
+
+    @property
+    def all_mailboxes(self):
+        if self[0].token_type == 'mailbox':
+            return [self[0]]
+        elif self[0].token_type == 'invalid-mailbox':
+            return [self[0]]
+        return self[0].all_mailboxes
+
+class MailboxList(TokenList):
+
+    token_type = 'mailbox-list'
+
+    @property
+    def mailboxes(self):
+        return [x for x in self if x.token_type=='mailbox']
+
+    @property
+    def all_mailboxes(self):
+        return [x for x in self
+            if x.token_type in ('mailbox', 'invalid-mailbox')]
+
+
+class GroupList(TokenList):
+
+    token_type = 'group-list'
+
+    @property
+    def mailboxes(self):
+        if not self or self[0].token_type != 'mailbox-list':
+            return []
+        return self[0].mailboxes
+
+    @property
+    def all_mailboxes(self):
+        if not self or self[0].token_type != 'mailbox-list':
+            return []
+        return self[0].all_mailboxes
+
+
+class Group(TokenList):
+
+    token_type = "group"
+
+    @property
+    def mailboxes(self):
+        if self[2].token_type != 'group-list':
+            return []
+        return self[2].mailboxes
+
+    @property
+    def all_mailboxes(self):
+        if self[2].token_type != 'group-list':
+            return []
+        return self[2].all_mailboxes
+
+    @property
+    def display_name(self):
+        return self[0].display_name
+
+
+class NameAddr(TokenList):
+
+    token_type = 'name-addr'
+
+    @property
+    def display_name(self):
+        if len(self) == 1:
+            return None
+        return self[0].display_name
+
+    @property
+    def local_part(self):
+        return self[-1].local_part
+
+    @property
+    def domain(self):
+        return self[-1].domain
+
+    @property
+    def route(self):
+        return self[-1].route
+
+    @property
+    def addr_spec(self):
+        return self[-1].addr_spec
+
+
+class AngleAddr(TokenList):
+
+    token_type = 'angle-addr'
+
+    @property
+    def local_part(self):
+        for x in self:
+            if x.token_type == 'addr-spec':
+                return x.local_part
+
+    @property
+    def domain(self):
+        for x in self:
+            if x.token_type == 'addr-spec':
+                return x.domain
+
+    @property
+    def route(self):
+        for x in self:
+            if x.token_type == 'obs-route':
+                return x.domains
+
+    @property
+    def addr_spec(self):
+        for x in self:
+            if x.token_type == 'addr-spec':
+                if x.local_part:
+                    return x.addr_spec
+                else:
+                    return quote_string(x.local_part) + x.addr_spec
+        else:
+            return '<>'
+
+
+class ObsRoute(TokenList):
+
+    token_type = 'obs-route'
+
+    @property
+    def domains(self):
+        return [x.domain for x in self if x.token_type == 'domain']
+
+
+class Mailbox(TokenList):
+
+    token_type = 'mailbox'
+
+    @property
+    def display_name(self):
+        if self[0].token_type == 'name-addr':
+            return self[0].display_name
+
+    @property
+    def local_part(self):
+        return self[0].local_part
+
+    @property
+    def domain(self):
+        return self[0].domain
+
+    @property
+    def route(self):
+        if self[0].token_type == 'name-addr':
+            return self[0].route
+
+    @property
+    def addr_spec(self):
+        return self[0].addr_spec
+
+
+class InvalidMailbox(TokenList):
+
+    token_type = 'invalid-mailbox'
+
+    @property
+    def display_name(self):
+        return None
+
+    local_part = domain = route = addr_spec = display_name
+
+
+class Domain(TokenList):
+
+    token_type = 'domain'
+    as_ew_allowed = False
+
+    @property
+    def domain(self):
+        return ''.join(super().value.split())
+
+
+class DotAtom(TokenList):
+
+    token_type = 'dot-atom'
+
+
+class DotAtomText(TokenList):
+
+    token_type = 'dot-atom-text'
+    as_ew_allowed = True
+
+
+class AddrSpec(TokenList):
+
+    token_type = 'addr-spec'
+    as_ew_allowed = False
+
+    @property
+    def local_part(self):
+        return self[0].local_part
+
+    @property
+    def domain(self):
+        if len(self) < 3:
+            return None
+        return self[-1].domain
+
+    @property
+    def value(self):
+        if len(self) < 3:
+            return self[0].value
+        return self[0].value.rstrip()+self[1].value+self[2].value.lstrip()
+
+    @property
+    def addr_spec(self):
+        nameset = set(self.local_part)
+        if len(nameset) > len(nameset-DOT_ATOM_ENDS):
+            lp = quote_string(self.local_part)
+        else:
+            lp = self.local_part
+        if self.domain is not None:
+            return lp + '@' + self.domain
+        return lp
+
+
+class ObsLocalPart(TokenList):
+
+    token_type = 'obs-local-part'
+    as_ew_allowed = False
+
+
+class DisplayName(Phrase):
+
+    token_type = 'display-name'
+    ew_combine_allowed = False
+
+    @property
+    def display_name(self):
+        res = TokenList(self)
+        if res[0].token_type == 'cfws':
+            res.pop(0)
+        else:
+            if res[0][0].token_type == 'cfws':
+                res[0] = TokenList(res[0][1:])
+        if res[-1].token_type == 'cfws':
+            res.pop()
+        else:
+            if res[-1][-1].token_type == 'cfws':
+                res[-1] = TokenList(res[-1][:-1])
+        return res.value
+
+    @property
+    def value(self):
+        quote = False
+        if self.defects:
+            quote = True
+        else:
+            for x in self:
+                if x.token_type == 'quoted-string':
+                    quote = True
+        if quote:
+            pre = post = ''
+            if self[0].token_type=='cfws' or self[0][0].token_type=='cfws':
+                pre = ' '
+            if self[-1].token_type=='cfws' or self[-1][-1].token_type=='cfws':
+                post = ' '
+            return pre+quote_string(self.display_name)+post
+        else:
+            return super().value
+
+
+class LocalPart(TokenList):
+
+    token_type = 'local-part'
+    as_ew_allowed = False
+
+    @property
+    def value(self):
+        if self[0].token_type == "quoted-string":
+            return self[0].quoted_value
+        else:
+            return self[0].value
+
+    @property
+    def local_part(self):
+        # Strip whitespace from front, back, and around dots.
+        res = [DOT]
+        last = DOT
+        last_is_tl = False
+        for tok in self[0] + [DOT]:
+            if tok.token_type == 'cfws':
+                continue
+            if (last_is_tl and tok.token_type == 'dot' and
+                    last[-1].token_type == 'cfws'):
+                res[-1] = TokenList(last[:-1])
+            is_tl = isinstance(tok, TokenList)
+            if (is_tl and last.token_type == 'dot' and
+                    tok[0].token_type == 'cfws'):
+                res.append(TokenList(tok[1:]))
+            else:
+                res.append(tok)
+            last = res[-1]
+            last_is_tl = is_tl
+        res = TokenList(res[1:-1])
+        return res.value
+
+
+class DomainLiteral(TokenList):
+
+    token_type = 'domain-literal'
+    as_ew_allowed = False
+
+    @property
+    def domain(self):
+        return ''.join(super().value.split())
+
+    @property
+    def ip(self):
+        for x in self:
+            if x.token_type == 'ptext':
+                return x.value
+
+
+class MIMEVersion(TokenList):
+
+    token_type = 'mime-version'
+    major = None
+    minor = None
+
+
+class Parameter(TokenList):
+
+    token_type = 'parameter'
+    sectioned = False
+    extended = False
+    charset = 'us-ascii'
+
+    @property
+    def section_number(self):
+        # Because the first token, the attribute (name) eats CFWS, the second
+        # token is always the section if there is one.
+        return self[1].number if self.sectioned else 0
+
+    @property
+    def param_value(self):
+        # This is part of the "handle quoted extended parameters" hack.
+        for token in self:
+            if token.token_type == 'value':
+                return token.stripped_value
+            if token.token_type == 'quoted-string':
+                for token in token:
+                    if token.token_type == 'bare-quoted-string':
+                        for token in token:
+                            if token.token_type == 'value':
+                                return token.stripped_value
+        return ''
+
+
+class InvalidParameter(Parameter):
+
+    token_type = 'invalid-parameter'
+
+
+class Attribute(TokenList):
+
+    token_type = 'attribute'
+
+    @property
+    def stripped_value(self):
+        for token in self:
+            if token.token_type.endswith('attrtext'):
+                return token.value
+
+class Section(TokenList):
+
+    token_type = 'section'
+    number = None
+
+
+class Value(TokenList):
+
+    token_type = 'value'
+
+    @property
+    def stripped_value(self):
+        token = self[0]
+        if token.token_type == 'cfws':
+            token = self[1]
+        if token.token_type.endswith(
+                ('quoted-string', 'attribute', 'extended-attribute')):
+            return token.stripped_value
+        return self.value
+
+
+class MimeParameters(TokenList):
+
+    token_type = 'mime-parameters'
+    syntactic_break = False
+
+    @property
+    def params(self):
+        # The RFC specifically states that the ordering of parameters is not
+        # guaranteed and may be reordered by the transport layer.  So we have
+        # to assume the RFC 2231 pieces can come in any order.  However, we
+        # output them in the order that we first see a given name, which gives
+        # us a stable __str__.
+        params = OrderedDict()
+        for token in self:
+            if not token.token_type.endswith('parameter'):
+                continue
+            if token[0].token_type != 'attribute':
+                continue
+            name = token[0].value.strip()
+            if name not in params:
+                params[name] = []
+            params[name].append((token.section_number, token))
+        for name, parts in params.items():
+            parts = sorted(parts, key=itemgetter(0))
+            first_param = parts[0][1]
+            charset = first_param.charset
+            # Our arbitrary error recovery is to ignore duplicate parameters,
+            # to use appearance order if there are duplicate rfc 2231 parts,
+            # and to ignore gaps.  This mimics the error recovery of get_param.
+            if not first_param.extended and len(parts) > 1:
+                if parts[1][0] == 0:
+                    parts[1][1].defects.append(errors.InvalidHeaderDefect(
+                        'duplicate parameter name; duplicate(s) ignored'))
+                    parts = parts[:1]
+                # Else assume the *0* was missing...note that this is different
+                # from get_param, but we registered a defect for this earlier.
+            value_parts = []
+            i = 0
+            for section_number, param in parts:
+                if section_number != i:
+                    # We could get fancier here and look for a complete
+                    # duplicate extended parameter and ignore the second one
+                    # seen.  But we're not doing that.  The old code didn't.
+                    if not param.extended:
+                        param.defects.append(errors.InvalidHeaderDefect(
+                            'duplicate parameter name; duplicate ignored'))
+                        continue
+                    else:
+                        param.defects.append(errors.InvalidHeaderDefect(
+                            "inconsistent RFC2231 parameter numbering"))
+                i += 1
+                value = param.param_value
+                if param.extended:
+                    try:
+                        value = parse.unquote_to_bytes(value)
+                    except UnicodeEncodeError:
+                        # source had surrogate escaped bytes.  What we do now
+                        # is a bit of an open question.  I'm not sure this is
+                        # the best choice, but it is what the old algorithm did
+                        value = parse.unquote(value, encoding='latin-1')
+                    else:
+                        try:
+                            value = value.decode(charset, 'surrogateescape')
+                        except LookupError:
+                            # XXX: there should really be a custom defect for
+                            # unknown character set to make it easy to find,
+                            # because otherwise unknown charset is a silent
+                            # failure.
+                            value = value.decode('us-ascii', 'surrogateescape')
+                        if utils._has_surrogates(value):
+                            param.defects.append(errors.UndecodableBytesDefect())
+                value_parts.append(value)
+            value = ''.join(value_parts)
+            yield name, value
+
+    def __str__(self):
+        params = []
+        for name, value in self.params:
+            if value:
+                params.append('{}={}'.format(name, quote_string(value)))
+            else:
+                params.append(name)
+        params = '; '.join(params)
+        return ' ' + params if params else ''
+
+
+class ParameterizedHeaderValue(TokenList):
+
+    # Set this false so that the value doesn't wind up on a new line even
+    # if it and the parameters would fit there but not on the first line.
+    syntactic_break = False
+
+    @property
+    def params(self):
+        for token in reversed(self):
+            if token.token_type == 'mime-parameters':
+                return token.params
+        return {}
+
+
+class ContentType(ParameterizedHeaderValue):
+
+    token_type = 'content-type'
+    as_ew_allowed = False
+    maintype = 'text'
+    subtype = 'plain'
+
+
+class ContentDisposition(ParameterizedHeaderValue):
+
+    token_type = 'content-disposition'
+    as_ew_allowed = False
+    content_disposition = None
+
+
+class ContentTransferEncoding(TokenList):
+
+    token_type = 'content-transfer-encoding'
+    as_ew_allowed = False
+    cte = '7bit'
+
+
+class HeaderLabel(TokenList):
+
+    token_type = 'header-label'
+    as_ew_allowed = False
+
+
+class Header(TokenList):
+
+    token_type = 'header'
+
+
+#
+# Terminal classes and instances
+#
+
+class Terminal(str):
+
+    as_ew_allowed = True
+    ew_combine_allowed = True
+    syntactic_break = True
+
+    def __new__(cls, value, token_type):
+        self = str.__newobj__(cls, value)
+        self.token_type = token_type
+        self.defects = []
+        return self
+
+    def __repr__(self):
+        return "{}({})".format(self.__class__.__name__, super().__repr__())
+
+    def pprint(self):
+        print(self.__class__.__name__ + '/' + self.token_type)
+
+    @property
+    def all_defects(self):
+        return list(self.defects)
+
+    def _pp(self, indent=''):
+        return ["{}{}/{}({}){}".format(
+            indent,
+            self.__class__.__name__,
+            self.token_type,
+            super().__repr__(),
+            '' if not self.defects else ' {}'.format(self.defects),
+            )]
+
+    def pop_trailing_ws(self):
+        # This terminates the recursion.
+        return None
+
+    @property
+    def comments(self):
+        return []
+
+    def __getnewargs__(self):
+        return(str(self), self.token_type)
+
+
+class WhiteSpaceTerminal(Terminal):
+
+    @property
+    def value(self):
+        return ' '
+
+    def startswith_fws(self):
+        return True
+
+
+class ValueTerminal(Terminal):
+
+    @property
+    def value(self):
+        return self
+
+    def startswith_fws(self):
+        return False
+
+
+class EWWhiteSpaceTerminal(WhiteSpaceTerminal):
+
+    @property
+    def value(self):
+        return ''
+
+    def __str__(self):
+        return ''
+
+
+# XXX these need to become classes and used as instances so
+# that a program can't change them in a parse tree and screw
+# up other parse trees.  Maybe should have  tests for that, too.
+DOT = ValueTerminal('.', 'dot')
+ListSeparator = ValueTerminal(',', 'list-separator')
+RouteComponentMarker = ValueTerminal('@', 'route-component-marker')
+
+#
+# Parser
+#
+
+# Parse strings according to RFC822/2047/2822/5322 rules.
+#
+# This is a stateless parser.  Each get_XXX function accepts a string and
+# returns either a Terminal or a TokenList representing the RFC object named
+# by the method and a string containing the remaining unparsed characters
+# from the input.  Thus a parser method consumes the next syntactic construct
+# of a given type and returns a token representing the construct plus the
+# unparsed remainder of the input string.
+#
+# For example, if the first element of a structured header is a 'phrase',
+# then:
+#
+#     phrase, value = get_phrase(value)
+#
+# returns the complete phrase from the start of the string value, plus any
+# characters left in the string after the phrase is removed.
+
+
+_wsp_splitter = re.compile(r'([{}]+)'.format(''.join(WSP))).split
+_non_atom_end_matcher = re.compile(r"[^{}]+".format(
+    ''.join(ATOM_ENDS).replace('\\','\\\\').replace(']',r'\]'))).match
+_non_printable_finder = re.compile(r"[\x00-\x20\x7F]").findall
+_non_token_end_matcher = re.compile(r"[^{}]+".format(
+    ''.join(TOKEN_ENDS).replace('\\','\\\\').replace(']',r'\]'))).match
+_non_attribute_end_matcher = re.compile(r"[^{}]+".format(
+    ''.join(ATTRIBUTE_ENDS).replace('\\','\\\\').replace(']',r'\]'))).match
+_non_extended_attribute_end_matcher = re.compile(r"[^{}]+".format(
+    ''.join(EXTENDED_ATTRIBUTE_ENDS).replace(
+                                    '\\','\\\\').replace(']',r'\]'))).match
+
+def _validate_xtext(xtext):
+    """If input token contains ASCII non-printables, register a defect."""
+
+    non_printables = _non_printable_finder(xtext)
+    if non_printables:
+        xtext.defects.append(errors.NonPrintableDefect(non_printables))
+    if utils._has_surrogates(xtext):
+        xtext.defects.append(errors.UndecodableBytesDefect(
+            "Non-ASCII characters found in header token"))
+
+def _get_ptext_to_endchars(value, endchars):
+    """Scan printables/quoted-pairs until endchars and return unquoted ptext.
+
+    This function turns a run of qcontent, ccontent-without-comments, or
+    dtext-with-quoted-printables into a single string by unquoting any
+    quoted printables.  It returns the string, the remaining value, and
+    a flag that is True iff there were any quoted printables decoded.
+
+    """
+    fragment, *remainder = _wsp_splitter(value, 1)
+    vchars = []
+    escape = False
+    had_qp = False
+    for pos in range(len(fragment)):
+        if fragment[pos] == '\\':
+            if escape:
+                escape = False
+                had_qp = True
+            else:
+                escape = True
+                continue
+        if escape:
+            escape = False
+        elif fragment[pos] in endchars:
+            break
+        vchars.append(fragment[pos])
+    else:
+        pos = pos + 1
+    return ''.join(vchars), ''.join([fragment[pos:]] + remainder), had_qp
+
+def get_fws(value):
+    """FWS = 1*WSP
+
+    This isn't the RFC definition.  We're using fws to represent tokens where
+    folding can be done, but when we are parsing the *un*folding has already
+    been done so we don't need to watch out for CRLF.
+
+    """
+    newvalue = value.lstrip()
+    fws = WhiteSpaceTerminal(value[:len(value)-len(newvalue)], 'fws')
+    return fws, newvalue
+
+def get_encoded_word(value):
+    """ encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
+
+    """
+    ew = EncodedWord()
+    if not value.startswith('=?'):
+        raise errors.HeaderParseError(
+            "expected encoded word but found {}".format(value))
+    tok, *remainder = value[2:].split('?=', 1)
+    if tok == value[2:]:
+        raise errors.HeaderParseError(
+            "expected encoded word but found {}".format(value))
+    remstr = ''.join(remainder)
+    if len(remstr) > 1 and remstr[0] in hexdigits and remstr[1] in hexdigits:
+        # The ? after the CTE was followed by an encoded word escape (=XX).
+        rest, *remainder = remstr.split('?=', 1)
+        tok = tok + '?=' + rest
+    if len(tok.split()) > 1:
+        ew.defects.append(errors.InvalidHeaderDefect(
+            "whitespace inside encoded word"))
+    ew.cte = value
+    value = ''.join(remainder)
+    try:
+        text, charset, lang, defects = _ew.decode('=?' + tok + '?=')
+    except ValueError:
+        raise errors.HeaderParseError(
+            "encoded word format invalid: '{}'".format(ew.cte))
+    ew.charset = charset
+    ew.lang = lang
+    ew.defects.extend(defects)
+    while text:
+        if text[0] in WSP:
+            token, text = get_fws(text)
+            ew.append(token)
+            continue
+        chars, *remainder = _wsp_splitter(text, 1)
+        vtext = ValueTerminal(chars, 'vtext')
+        _validate_xtext(vtext)
+        ew.append(vtext)
+        text = ''.join(remainder)
+    return ew, value
+
+def get_unstructured(value):
+    """unstructured = (*([FWS] vchar) *WSP) / obs-unstruct
+       obs-unstruct = *((*LF *CR *(obs-utext) *LF *CR)) / FWS)
+       obs-utext = %d0 / obs-NO-WS-CTL / LF / CR
+
+       obs-NO-WS-CTL is control characters except WSP/CR/LF.
+
+    So, basically, we have printable runs, plus control characters or nulls in
+    the obsolete syntax, separated by whitespace.  Since RFC 2047 uses the
+    obsolete syntax in its specification, but requires whitespace on either
+    side of the encoded words, I can see no reason to need to separate the
+    non-printable-non-whitespace from the printable runs if they occur, so we
+    parse this into xtext tokens separated by WSP tokens.
+
+    Because an 'unstructured' value must by definition constitute the entire
+    value, this 'get' routine does not return a remaining value, only the
+    parsed TokenList.
+
+    """
+    # XXX: but what about bare CR and LF?  They might signal the start or
+    # end of an encoded word.  YAGNI for now, since our current parsers
+    # will never send us strings with bare CR or LF.
+
+    unstructured = UnstructuredTokenList()
+    while value:
+        if value[0] in WSP:
+            token, value = get_fws(value)
+            unstructured.append(token)
+            continue
+        if value.startswith('=?'):
+            try:
+                token, value = get_encoded_word(value)
+            except errors.HeaderParseError:
+                # XXX: Need to figure out how to register defects when
+                # appropriate here.
+                pass
+            else:
+                have_ws = True
+                if len(unstructured) > 0:
+                    if unstructured[-1].token_type != 'fws':
+                        unstructured.defects.append(errors.InvalidHeaderDefect(
+                            "missing whitespace before encoded word"))
+                        have_ws = False
+                if have_ws and len(unstructured) > 1:
+                    if unstructured[-2].token_type == 'encoded-word':
+                        unstructured[-1] = EWWhiteSpaceTerminal(
+                            unstructured[-1], 'fws')
+                unstructured.append(token)
+                continue
+        tok, *remainder = _wsp_splitter(value, 1)
+        vtext = ValueTerminal(tok, 'vtext')
+        _validate_xtext(vtext)
+        unstructured.append(vtext)
+        value = ''.join(remainder)
+    return unstructured
+
+def get_qp_ctext(value):
+    r"""ctext = <printable ascii except \ ( )>
+
+    This is not the RFC ctext, since we are handling nested comments in comment
+    and unquoting quoted-pairs here.  We allow anything except the '()'
+    characters, but if we find any ASCII other than the RFC defined printable
+    ASCII, a NonPrintableDefect is added to the token's defects list.  Since
+    quoted pairs are converted to their unquoted values, what is returned is
+    a 'ptext' token.  In this case it is a WhiteSpaceTerminal, so it's value
+    is ' '.
+
+    """
+    ptext, value, _ = _get_ptext_to_endchars(value, '()')
+    ptext = WhiteSpaceTerminal(ptext, 'ptext')
+    _validate_xtext(ptext)
+    return ptext, value
+
+def get_qcontent(value):
+    """qcontent = qtext / quoted-pair
+
+    We allow anything except the DQUOTE character, but if we find any ASCII
+    other than the RFC defined printable ASCII, a NonPrintableDefect is
+    added to the token's defects list.  Any quoted pairs are converted to their
+    unquoted values, so what is returned is a 'ptext' token.  In this case it
+    is a ValueTerminal.
+
+    """
+    ptext, value, _ = _get_ptext_to_endchars(value, '"')
+    ptext = ValueTerminal(ptext, 'ptext')
+    _validate_xtext(ptext)
+    return ptext, value
+
+def get_atext(value):
+    """atext = <matches _atext_matcher>
+
+    We allow any non-ATOM_ENDS in atext, but add an InvalidATextDefect to
+    the token's defects list if we find non-atext characters.
+    """
+    m = _non_atom_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected atext but found '{}'".format(value))
+    atext = m.group()
+    value = value[len(atext):]
+    atext = ValueTerminal(atext, 'atext')
+    _validate_xtext(atext)
+    return atext, value
+
+def get_bare_quoted_string(value):
+    """bare-quoted-string = DQUOTE *([FWS] qcontent) [FWS] DQUOTE
+
+    A quoted-string without the leading or trailing white space.  Its
+    value is the text between the quote marks, with whitespace
+    preserved and quoted pairs decoded.
+    """
+    if value[0] != '"':
+        raise errors.HeaderParseError(
+            "expected '\"' but found '{}'".format(value))
+    bare_quoted_string = BareQuotedString()
+    value = value[1:]
+    if value[0] == '"':
+        token, value = get_qcontent(value)
+        bare_quoted_string.append(token)
+    while value and value[0] != '"':
+        if value[0] in WSP:
+            token, value = get_fws(value)
+        elif value[:2] == '=?':
+            try:
+                token, value = get_encoded_word(value)
+                bare_quoted_string.defects.append(errors.InvalidHeaderDefect(
+                    "encoded word inside quoted string"))
+            except errors.HeaderParseError:
+                token, value = get_qcontent(value)
+        else:
+            token, value = get_qcontent(value)
+        bare_quoted_string.append(token)
+    if not value:
+        bare_quoted_string.defects.append(errors.InvalidHeaderDefect(
+            "end of header inside quoted string"))
+        return bare_quoted_string, value
+    return bare_quoted_string, value[1:]
+
+def get_comment(value):
+    """comment = "(" *([FWS] ccontent) [FWS] ")"
+       ccontent = ctext / quoted-pair / comment
+
+    We handle nested comments here, and quoted-pair in our qp-ctext routine.
+    """
+    if value and value[0] != '(':
+        raise errors.HeaderParseError(
+            "expected '(' but found '{}'".format(value))
+    comment = Comment()
+    value = value[1:]
+    while value and value[0] != ")":
+        if value[0] in WSP:
+            token, value = get_fws(value)
+        elif value[0] == '(':
+            token, value = get_comment(value)
+        else:
+            token, value = get_qp_ctext(value)
+        comment.append(token)
+    if not value:
+        comment.defects.append(errors.InvalidHeaderDefect(
+            "end of header inside comment"))
+        return comment, value
+    return comment, value[1:]
+
+def get_cfws(value):
+    """CFWS = (1*([FWS] comment) [FWS]) / FWS
+
+    """
+    cfws = CFWSList()
+    while value and value[0] in CFWS_LEADER:
+        if value[0] in WSP:
+            token, value = get_fws(value)
+        else:
+            token, value = get_comment(value)
+        cfws.append(token)
+    return cfws, value
+
+def get_quoted_string(value):
+    """quoted-string = [CFWS] <bare-quoted-string> [CFWS]
+
+    'bare-quoted-string' is an intermediate class defined by this
+    parser and not by the RFC grammar.  It is the quoted string
+    without any attached CFWS.
+    """
+    quoted_string = QuotedString()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        quoted_string.append(token)
+    token, value = get_bare_quoted_string(value)
+    quoted_string.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        quoted_string.append(token)
+    return quoted_string, value
+
+def get_atom(value):
+    """atom = [CFWS] 1*atext [CFWS]
+
+    An atom could be an rfc2047 encoded word.
+    """
+    atom = Atom()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        atom.append(token)
+    if value and value[0] in ATOM_ENDS:
+        raise errors.HeaderParseError(
+            "expected atom but found '{}'".format(value))
+    if value.startswith('=?'):
+        try:
+            token, value = get_encoded_word(value)
+        except errors.HeaderParseError:
+            # XXX: need to figure out how to register defects when
+            # appropriate here.
+            token, value = get_atext(value)
+    else:
+        token, value = get_atext(value)
+    atom.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        atom.append(token)
+    return atom, value
+
+def get_dot_atom_text(value):
+    """ dot-text = 1*atext *("." 1*atext)
+
+    """
+    dot_atom_text = DotAtomText()
+    if not value or value[0] in ATOM_ENDS:
+        raise errors.HeaderParseError("expected atom at a start of "
+            "dot-atom-text but found '{}'".format(value))
+    while value and value[0] not in ATOM_ENDS:
+        token, value = get_atext(value)
+        dot_atom_text.append(token)
+        if value and value[0] == '.':
+            dot_atom_text.append(DOT)
+            value = value[1:]
+    if dot_atom_text[-1] is DOT:
+        raise errors.HeaderParseError("expected atom at end of dot-atom-text "
+            "but found '{}'".format('.'+value))
+    return dot_atom_text, value
+
+def get_dot_atom(value):
+    """ dot-atom = [CFWS] dot-atom-text [CFWS]
+
+    Any place we can have a dot atom, we could instead have an rfc2047 encoded
+    word.
+    """
+    dot_atom = DotAtom()
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        dot_atom.append(token)
+    if value.startswith('=?'):
+        try:
+            token, value = get_encoded_word(value)
+        except errors.HeaderParseError:
+            # XXX: need to figure out how to register defects when
+            # appropriate here.
+            token, value = get_dot_atom_text(value)
+    else:
+        token, value = get_dot_atom_text(value)
+    dot_atom.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        dot_atom.append(token)
+    return dot_atom, value
+
+def get_word(value):
+    """word = atom / quoted-string
+
+    Either atom or quoted-string may start with CFWS.  We have to peel off this
+    CFWS first to determine which type of word to parse.  Afterward we splice
+    the leading CFWS, if any, into the parsed sub-token.
+
+    If neither an atom or a quoted-string is found before the next special, a
+    HeaderParseError is raised.
+
+    The token returned is either an Atom or a QuotedString, as appropriate.
+    This means the 'word' level of the formal grammar is not represented in the
+    parse tree; this is because having that extra layer when manipulating the
+    parse tree is more confusing than it is helpful.
+
+    """
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    else:
+        leader = None
+    if value[0]=='"':
+        token, value = get_quoted_string(value)
+    elif value[0] in SPECIALS:
+        raise errors.HeaderParseError("Expected 'atom' or 'quoted-string' "
+                                      "but found '{}'".format(value))
+    else:
+        token, value = get_atom(value)
+    if leader is not None:
+        token[:0] = [leader]
+    return token, value
+
+def get_phrase(value):
+    """ phrase = 1*word / obs-phrase
+        obs-phrase = word *(word / "." / CFWS)
+
+    This means a phrase can be a sequence of words, periods, and CFWS in any
+    order as long as it starts with at least one word.  If anything other than
+    words is detected, an ObsoleteHeaderDefect is added to the token's defect
+    list.  We also accept a phrase that starts with CFWS followed by a dot;
+    this is registered as an InvalidHeaderDefect, since it is not supported by
+    even the obsolete grammar.
+
+    """
+    phrase = Phrase()
+    try:
+        token, value = get_word(value)
+        phrase.append(token)
+    except errors.HeaderParseError:
+        phrase.defects.append(errors.InvalidHeaderDefect(
+            "phrase does not start with word"))
+    while value and value[0] not in PHRASE_ENDS:
+        if value[0]=='.':
+            phrase.append(DOT)
+            phrase.defects.append(errors.ObsoleteHeaderDefect(
+                "period in 'phrase'"))
+            value = value[1:]
+        else:
+            try:
+                token, value = get_word(value)
+            except errors.HeaderParseError:
+                if value[0] in CFWS_LEADER:
+                    token, value = get_cfws(value)
+                    phrase.defects.append(errors.ObsoleteHeaderDefect(
+                        "comment found without atom"))
+                else:
+                    raise
+            phrase.append(token)
+    return phrase, value
+
+def get_local_part(value):
+    """ local-part = dot-atom / quoted-string / obs-local-part
+
+    """
+    local_part = LocalPart()
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    if not value:
+        raise errors.HeaderParseError(
+            "expected local-part but found '{}'".format(value))
+    try:
+        token, value = get_dot_atom(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_word(value)
+        except errors.HeaderParseError:
+            if value[0] != '\\' and value[0] in PHRASE_ENDS:
+                raise
+            token = TokenList()
+    if leader is not None:
+        token[:0] = [leader]
+    local_part.append(token)
+    if value and (value[0]=='\\' or value[0] not in PHRASE_ENDS):
+        obs_local_part, value = get_obs_local_part(str(local_part) + value)
+        if obs_local_part.token_type == 'invalid-obs-local-part':
+            local_part.defects.append(errors.InvalidHeaderDefect(
+                "local-part is not dot-atom, quoted-string, or obs-local-part"))
+        else:
+            local_part.defects.append(errors.ObsoleteHeaderDefect(
+                "local-part is not a dot-atom (contains CFWS)"))
+        local_part[0] = obs_local_part
+    try:
+        local_part.value.encode('ascii')
+    except UnicodeEncodeError:
+        local_part.defects.append(errors.NonASCIILocalPartDefect(
+                "local-part contains non-ASCII characters)"))
+    return local_part, value
+
+def get_obs_local_part(value):
+    """ obs-local-part = word *("." word)
+    """
+    obs_local_part = ObsLocalPart()
+    last_non_ws_was_dot = False
+    while value and (value[0]=='\\' or value[0] not in PHRASE_ENDS):
+        if value[0] == '.':
+            if last_non_ws_was_dot:
+                obs_local_part.defects.append(errors.InvalidHeaderDefect(
+                    "invalid repeated '.'"))
+            obs_local_part.append(DOT)
+            last_non_ws_was_dot = True
+            value = value[1:]
+            continue
+        elif value[0]=='\\':
+            obs_local_part.append(ValueTerminal(value[0],
+                                                'misplaced-special'))
+            value = value[1:]
+            obs_local_part.defects.append(errors.InvalidHeaderDefect(
+                "'\\' character outside of quoted-string/ccontent"))
+            last_non_ws_was_dot = False
+            continue
+        if obs_local_part and obs_local_part[-1].token_type != 'dot':
+            obs_local_part.defects.append(errors.InvalidHeaderDefect(
+                "missing '.' between words"))
+        try:
+            token, value = get_word(value)
+            last_non_ws_was_dot = False
+        except errors.HeaderParseError:
+            if value[0] not in CFWS_LEADER:
+                raise
+            token, value = get_cfws(value)
+        obs_local_part.append(token)
+    if (obs_local_part[0].token_type == 'dot' or
+            obs_local_part[0].token_type=='cfws' and
+            obs_local_part[1].token_type=='dot'):
+        obs_local_part.defects.append(errors.InvalidHeaderDefect(
+            "Invalid leading '.' in local part"))
+    if (obs_local_part[-1].token_type == 'dot' or
+            obs_local_part[-1].token_type=='cfws' and
+            obs_local_part[-2].token_type=='dot'):
+        obs_local_part.defects.append(errors.InvalidHeaderDefect(
+            "Invalid trailing '.' in local part"))
+    if obs_local_part.defects:
+        obs_local_part.token_type = 'invalid-obs-local-part'
+    return obs_local_part, value
+
+def get_dtext(value):
+    r""" dtext = <printable ascii except \ [ ]> / obs-dtext
+        obs-dtext = obs-NO-WS-CTL / quoted-pair
+
+    We allow anything except the excluded characters, but if we find any
+    ASCII other than the RFC defined printable ASCII, a NonPrintableDefect is
+    added to the token's defects list.  Quoted pairs are converted to their
+    unquoted values, so what is returned is a ptext token, in this case a
+    ValueTerminal.  If there were quoted-printables, an ObsoleteHeaderDefect is
+    added to the returned token's defect list.
+
+    """
+    ptext, value, had_qp = _get_ptext_to_endchars(value, '[]')
+    ptext = ValueTerminal(ptext, 'ptext')
+    if had_qp:
+        ptext.defects.append(errors.ObsoleteHeaderDefect(
+            "quoted printable found in domain-literal"))
+    _validate_xtext(ptext)
+    return ptext, value
+
+def _check_for_early_dl_end(value, domain_literal):
+    if value:
+        return False
+    domain_literal.append(errors.InvalidHeaderDefect(
+        "end of input inside domain-literal"))
+    domain_literal.append(ValueTerminal(']', 'domain-literal-end'))
+    return True
+
+def get_domain_literal(value):
+    """ domain-literal = [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
+
+    """
+    domain_literal = DomainLiteral()
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        domain_literal.append(token)
+    if not value:
+        raise errors.HeaderParseError("expected domain-literal")
+    if value[0] != '[':
+        raise errors.HeaderParseError("expected '[' at start of domain-literal "
+                "but found '{}'".format(value))
+    value = value[1:]
+    if _check_for_early_dl_end(value, domain_literal):
+        return domain_literal, value
+    domain_literal.append(ValueTerminal('[', 'domain-literal-start'))
+    if value[0] in WSP:
+        token, value = get_fws(value)
+        domain_literal.append(token)
+    token, value = get_dtext(value)
+    domain_literal.append(token)
+    if _check_for_early_dl_end(value, domain_literal):
+        return domain_literal, value
+    if value[0] in WSP:
+        token, value = get_fws(value)
+        domain_literal.append(token)
+    if _check_for_early_dl_end(value, domain_literal):
+        return domain_literal, value
+    if value[0] != ']':
+        raise errors.HeaderParseError("expected ']' at end of domain-literal "
+                "but found '{}'".format(value))
+    domain_literal.append(ValueTerminal(']', 'domain-literal-end'))
+    value = value[1:]
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        domain_literal.append(token)
+    return domain_literal, value
+
+def get_domain(value):
+    """ domain = dot-atom / domain-literal / obs-domain
+        obs-domain = atom *("." atom))
+
+    """
+    domain = Domain()
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    if not value:
+        raise errors.HeaderParseError(
+            "expected domain but found '{}'".format(value))
+    if value[0] == '[':
+        token, value = get_domain_literal(value)
+        if leader is not None:
+            token[:0] = [leader]
+        domain.append(token)
+        return domain, value
+    try:
+        token, value = get_dot_atom(value)
+    except errors.HeaderParseError:
+        token, value = get_atom(value)
+    if leader is not None:
+        token[:0] = [leader]
+    domain.append(token)
+    if value and value[0] == '.':
+        domain.defects.append(errors.ObsoleteHeaderDefect(
+            "domain is not a dot-atom (contains CFWS)"))
+        if domain[0].token_type == 'dot-atom':
+            domain[:] = domain[0]
+        while value and value[0] == '.':
+            domain.append(DOT)
+            token, value = get_atom(value[1:])
+            domain.append(token)
+    return domain, value
+
+def get_addr_spec(value):
+    """ addr-spec = local-part "@" domain
+
+    """
+    addr_spec = AddrSpec()
+    token, value = get_local_part(value)
+    addr_spec.append(token)
+    if not value or value[0] != '@':
+        addr_spec.defects.append(errors.InvalidHeaderDefect(
+            "add-spec local part with no domain"))
+        return addr_spec, value
+    addr_spec.append(ValueTerminal('@', 'address-at-symbol'))
+    token, value = get_domain(value[1:])
+    addr_spec.append(token)
+    return addr_spec, value
+
+def get_obs_route(value):
+    """ obs-route = obs-domain-list ":"
+        obs-domain-list = *(CFWS / ",") "@" domain *("," [CFWS] ["@" domain])
+
+        Returns an obs-route token with the appropriate sub-tokens (that is,
+        there is no obs-domain-list in the parse tree).
+    """
+    obs_route = ObsRoute()
+    while value and (value[0]==',' or value[0] in CFWS_LEADER):
+        if value[0] in CFWS_LEADER:
+            token, value = get_cfws(value)
+            obs_route.append(token)
+        elif value[0] == ',':
+            obs_route.append(ListSeparator)
+            value = value[1:]
+    if not value or value[0] != '@':
+        raise errors.HeaderParseError(
+            "expected obs-route domain but found '{}'".format(value))
+    obs_route.append(RouteComponentMarker)
+    token, value = get_domain(value[1:])
+    obs_route.append(token)
+    while value and value[0]==',':
+        obs_route.append(ListSeparator)
+        value = value[1:]
+        if not value:
+            break
+        if value[0] in CFWS_LEADER:
+            token, value = get_cfws(value)
+            obs_route.append(token)
+        if value[0] == '@':
+            obs_route.append(RouteComponentMarker)
+            token, value = get_domain(value[1:])
+            obs_route.append(token)
+    if not value:
+        raise errors.HeaderParseError("end of header while parsing obs-route")
+    if value[0] != ':':
+        raise errors.HeaderParseError( "expected ':' marking end of "
+            "obs-route but found '{}'".format(value))
+    obs_route.append(ValueTerminal(':', 'end-of-obs-route-marker'))
+    return obs_route, value[1:]
+
+def get_angle_addr(value):
+    """ angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
+        obs-angle-addr = [CFWS] "<" obs-route addr-spec ">" [CFWS]
+
+    """
+    angle_addr = AngleAddr()
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        angle_addr.append(token)
+    if not value or value[0] != '<':
+        raise errors.HeaderParseError(
+            "expected angle-addr but found '{}'".format(value))
+    angle_addr.append(ValueTerminal('<', 'angle-addr-start'))
+    value = value[1:]
+    # Although it is not legal per RFC5322, SMTP uses '<>' in certain
+    # circumstances.
+    if value[0] == '>':
+        angle_addr.append(ValueTerminal('>', 'angle-addr-end'))
+        angle_addr.defects.append(errors.InvalidHeaderDefect(
+            "null addr-spec in angle-addr"))
+        value = value[1:]
+        return angle_addr, value
+    try:
+        token, value = get_addr_spec(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_obs_route(value)
+            angle_addr.defects.append(errors.ObsoleteHeaderDefect(
+                "obsolete route specification in angle-addr"))
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected addr-spec or obs-route but found '{}'".format(value))
+        angle_addr.append(token)
+        token, value = get_addr_spec(value)
+    angle_addr.append(token)
+    if value and value[0] == '>':
+        value = value[1:]
+    else:
+        angle_addr.defects.append(errors.InvalidHeaderDefect(
+            "missing trailing '>' on angle-addr"))
+    angle_addr.append(ValueTerminal('>', 'angle-addr-end'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        angle_addr.append(token)
+    return angle_addr, value
+
+def get_display_name(value):
+    """ display-name = phrase
+
+    Because this is simply a name-rule, we don't return a display-name
+    token containing a phrase, but rather a display-name token with
+    the content of the phrase.
+
+    """
+    display_name = DisplayName()
+    token, value = get_phrase(value)
+    display_name.extend(token[:])
+    display_name.defects = token.defects[:]
+    return display_name, value
+
+
+def get_name_addr(value):
+    """ name-addr = [display-name] angle-addr
+
+    """
+    name_addr = NameAddr()
+    # Both the optional display name and the angle-addr can start with cfws.
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+        if not value:
+            raise errors.HeaderParseError(
+                "expected name-addr but found '{}'".format(leader))
+    if value[0] != '<':
+        if value[0] in PHRASE_ENDS:
+            raise errors.HeaderParseError(
+                "expected name-addr but found '{}'".format(value))
+        token, value = get_display_name(value)
+        if not value:
+            raise errors.HeaderParseError(
+                "expected name-addr but found '{}'".format(token))
+        if leader is not None:
+            token[0][:0] = [leader]
+            leader = None
+        name_addr.append(token)
+    token, value = get_angle_addr(value)
+    if leader is not None:
+        token[:0] = [leader]
+    name_addr.append(token)
+    return name_addr, value
+
+def get_mailbox(value):
+    """ mailbox = name-addr / addr-spec
+
+    """
+    # The only way to figure out if we are dealing with a name-addr or an
+    # addr-spec is to try parsing each one.
+    mailbox = Mailbox()
+    try:
+        token, value = get_name_addr(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_addr_spec(value)
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected mailbox but found '{}'".format(value))
+    if any(isinstance(x, errors.InvalidHeaderDefect)
+                       for x in token.all_defects):
+        mailbox.token_type = 'invalid-mailbox'
+    mailbox.append(token)
+    return mailbox, value
+
+def get_invalid_mailbox(value, endchars):
+    """ Read everything up to one of the chars in endchars.
+
+    This is outside the formal grammar.  The InvalidMailbox TokenList that is
+    returned acts like a Mailbox, but the data attributes are None.
+
+    """
+    invalid_mailbox = InvalidMailbox()
+    while value and value[0] not in endchars:
+        if value[0] in PHRASE_ENDS:
+            invalid_mailbox.append(ValueTerminal(value[0],
+                                                 'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            invalid_mailbox.append(token)
+    return invalid_mailbox, value
+
+def get_mailbox_list(value):
+    """ mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
+        obs-mbox-list = *([CFWS] ",") mailbox *("," [mailbox / CFWS])
+
+    For this routine we go outside the formal grammar in order to improve error
+    handling.  We recognize the end of the mailbox list only at the end of the
+    value or at a ';' (the group terminator).  This is so that we can turn
+    invalid mailboxes into InvalidMailbox tokens and continue parsing any
+    remaining valid mailboxes.  We also allow all mailbox entries to be null,
+    and this condition is handled appropriately at a higher level.
+
+    """
+    mailbox_list = MailboxList()
+    while value and value[0] != ';':
+        try:
+            token, value = get_mailbox(value)
+            mailbox_list.append(token)
+        except errors.HeaderParseError:
+            leader = None
+            if value[0] in CFWS_LEADER:
+                leader, value = get_cfws(value)
+                if not value or value[0] in ',;':
+                    mailbox_list.append(leader)
+                    mailbox_list.defects.append(errors.ObsoleteHeaderDefect(
+                        "empty element in mailbox-list"))
+                else:
+                    token, value = get_invalid_mailbox(value, ',;')
+                    if leader is not None:
+                        token[:0] = [leader]
+                    mailbox_list.append(token)
+                    mailbox_list.defects.append(errors.InvalidHeaderDefect(
+                        "invalid mailbox in mailbox-list"))
+            elif value[0] == ',':
+                mailbox_list.defects.append(errors.ObsoleteHeaderDefect(
+                    "empty element in mailbox-list"))
+            else:
+                token, value = get_invalid_mailbox(value, ',;')
+                if leader is not None:
+                    token[:0] = [leader]
+                mailbox_list.append(token)
+                mailbox_list.defects.append(errors.InvalidHeaderDefect(
+                    "invalid mailbox in mailbox-list"))
+        if value and value[0] not in ',;':
+            # Crap after mailbox; treat it as an invalid mailbox.
+            # The mailbox info will still be available.
+            mailbox = mailbox_list[-1]
+            mailbox.token_type = 'invalid-mailbox'
+            token, value = get_invalid_mailbox(value, ',;')
+            mailbox.extend(token)
+            mailbox_list.defects.append(errors.InvalidHeaderDefect(
+                "invalid mailbox in mailbox-list"))
+        if value and value[0] == ',':
+            mailbox_list.append(ListSeparator)
+            value = value[1:]
+    return mailbox_list, value
+
+
+def get_group_list(value):
+    """ group-list = mailbox-list / CFWS / obs-group-list
+        obs-group-list = 1*([CFWS] ",") [CFWS]
+
+    """
+    group_list = GroupList()
+    if not value:
+        group_list.defects.append(errors.InvalidHeaderDefect(
+            "end of header before group-list"))
+        return group_list, value
+    leader = None
+    if value and value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+        if not value:
+            # This should never happen in email parsing, since CFWS-only is a
+            # legal alternative to group-list in a group, which is the only
+            # place group-list appears.
+            group_list.defects.append(errors.InvalidHeaderDefect(
+                "end of header in group-list"))
+            group_list.append(leader)
+            return group_list, value
+        if value[0] == ';':
+            group_list.append(leader)
+            return group_list, value
+    token, value = get_mailbox_list(value)
+    if len(token.all_mailboxes)==0:
+        if leader is not None:
+            group_list.append(leader)
+        group_list.extend(token)
+        group_list.defects.append(errors.ObsoleteHeaderDefect(
+            "group-list with empty entries"))
+        return group_list, value
+    if leader is not None:
+        token[:0] = [leader]
+    group_list.append(token)
+    return group_list, value
+
+def get_group(value):
+    """ group = display-name ":" [group-list] ";" [CFWS]
+
+    """
+    group = Group()
+    token, value = get_display_name(value)
+    if not value or value[0] != ':':
+        raise errors.HeaderParseError("expected ':' at end of group "
+            "display name but found '{}'".format(value))
+    group.append(token)
+    group.append(ValueTerminal(':', 'group-display-name-terminator'))
+    value = value[1:]
+    if value and value[0] == ';':
+        group.append(ValueTerminal(';', 'group-terminator'))
+        return group, value[1:]
+    token, value = get_group_list(value)
+    group.append(token)
+    if not value:
+        group.defects.append(errors.InvalidHeaderDefect(
+            "end of header in group"))
+    if value[0] != ';':
+        raise errors.HeaderParseError(
+            "expected ';' at end of group but found {}".format(value))
+    group.append(ValueTerminal(';', 'group-terminator'))
+    value = value[1:]
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        group.append(token)
+    return group, value
+
+def get_address(value):
+    """ address = mailbox / group
+
+    Note that counter-intuitively, an address can be either a single address or
+    a list of addresses (a group).  This is why the returned Address object has
+    a 'mailboxes' attribute which treats a single address as a list of length
+    one.  When you need to differentiate between to two cases, extract the single
+    element, which is either a mailbox or a group token.
+
+    """
+    # The formal grammar isn't very helpful when parsing an address.  mailbox
+    # and group, especially when allowing for obsolete forms, start off very
+    # similarly.  It is only when you reach one of @, <, or : that you know
+    # what you've got.  So, we try each one in turn, starting with the more
+    # likely of the two.  We could perhaps make this more efficient by looking
+    # for a phrase and then branching based on the next character, but that
+    # would be a premature optimization.
+    address = Address()
+    try:
+        token, value = get_group(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_mailbox(value)
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected address but found '{}'".format(value))
+    address.append(token)
+    return address, value
+
+def get_address_list(value):
+    """ address_list = (address *("," address)) / obs-addr-list
+        obs-addr-list = *([CFWS] ",") address *("," [address / CFWS])
+
+    We depart from the formal grammar here by continuing to parse until the end
+    of the input, assuming the input to be entirely composed of an
+    address-list.  This is always true in email parsing, and allows us
+    to skip invalid addresses to parse additional valid ones.
+
+    """
+    address_list = AddressList()
+    while value:
+        try:
+            token, value = get_address(value)
+            address_list.append(token)
+        except errors.HeaderParseError as err:
+            leader = None
+            if value[0] in CFWS_LEADER:
+                leader, value = get_cfws(value)
+                if not value or value[0] == ',':
+                    address_list.append(leader)
+                    address_list.defects.append(errors.ObsoleteHeaderDefect(
+                        "address-list entry with no content"))
+                else:
+                    token, value = get_invalid_mailbox(value, ',')
+                    if leader is not None:
+                        token[:0] = [leader]
+                    address_list.append(Address([token]))
+                    address_list.defects.append(errors.InvalidHeaderDefect(
+                        "invalid address in address-list"))
+            elif value[0] == ',':
+                address_list.defects.append(errors.ObsoleteHeaderDefect(
+                    "empty element in address-list"))
+            else:
+                token, value = get_invalid_mailbox(value, ',')
+                if leader is not None:
+                    token[:0] = [leader]
+                address_list.append(Address([token]))
+                address_list.defects.append(errors.InvalidHeaderDefect(
+                    "invalid address in address-list"))
+        if value and value[0] != ',':
+            # Crap after address; treat it as an invalid mailbox.
+            # The mailbox info will still be available.
+            mailbox = address_list[-1][0]
+            mailbox.token_type = 'invalid-mailbox'
+            token, value = get_invalid_mailbox(value, ',')
+            mailbox.extend(token)
+            address_list.defects.append(errors.InvalidHeaderDefect(
+                "invalid address in address-list"))
+        if value:  # Must be a , at this point.
+            address_list.append(ValueTerminal(',', 'list-separator'))
+            value = value[1:]
+    return address_list, value
+
+#
+# XXX: As I begin to add additional header parsers, I'm realizing we probably
+# have two level of parser routines: the get_XXX methods that get a token in
+# the grammar, and parse_XXX methods that parse an entire field value.  So
+# get_address_list above should really be a parse_ method, as probably should
+# be get_unstructured.
+#
+
+def parse_mime_version(value):
+    """ mime-version = [CFWS] 1*digit [CFWS] "." [CFWS] 1*digit [CFWS]
+
+    """
+    # The [CFWS] is implicit in the RFC 2045 BNF.
+    # XXX: This routine is a bit verbose, should factor out a get_int method.
+    mime_version = MIMEVersion()
+    if not value:
+        mime_version.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing MIME version number (eg: 1.0)"))
+        return mime_version
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+        if not value:
+            mime_version.defects.append(errors.HeaderMissingRequiredValue(
+                "Expected MIME version number but found only CFWS"))
+    digits = ''
+    while value and value[0] != '.' and value[0] not in CFWS_LEADER:
+        digits += value[0]
+        value = value[1:]
+    if not digits.isdigit():
+        mime_version.defects.append(errors.InvalidHeaderDefect(
+            "Expected MIME major version number but found {!r}".format(digits)))
+        mime_version.append(ValueTerminal(digits, 'xtext'))
+    else:
+        mime_version.major = int(digits)
+        mime_version.append(ValueTerminal(digits, 'digits'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+    if not value or value[0] != '.':
+        if mime_version.major is not None:
+            mime_version.defects.append(errors.InvalidHeaderDefect(
+                "Incomplete MIME version; found only major number"))
+        if value:
+            mime_version.append(ValueTerminal(value, 'xtext'))
+        return mime_version
+    mime_version.append(ValueTerminal('.', 'version-separator'))
+    value = value[1:]
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+    if not value:
+        if mime_version.major is not None:
+            mime_version.defects.append(errors.InvalidHeaderDefect(
+                "Incomplete MIME version; found only major number"))
+        return mime_version
+    digits = ''
+    while value and value[0] not in CFWS_LEADER:
+        digits += value[0]
+        value = value[1:]
+    if not digits.isdigit():
+        mime_version.defects.append(errors.InvalidHeaderDefect(
+            "Expected MIME minor version number but found {!r}".format(digits)))
+        mime_version.append(ValueTerminal(digits, 'xtext'))
+    else:
+        mime_version.minor = int(digits)
+        mime_version.append(ValueTerminal(digits, 'digits'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+    if value:
+        mime_version.defects.append(errors.InvalidHeaderDefect(
+            "Excess non-CFWS text after MIME version"))
+        mime_version.append(ValueTerminal(value, 'xtext'))
+    return mime_version
+
+def get_invalid_parameter(value):
+    """ Read everything up to the next ';'.
+
+    This is outside the formal grammar.  The InvalidParameter TokenList that is
+    returned acts like a Parameter, but the data attributes are None.
+
+    """
+    invalid_parameter = InvalidParameter()
+    while value and value[0] != ';':
+        if value[0] in PHRASE_ENDS:
+            invalid_parameter.append(ValueTerminal(value[0],
+                                                   'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            invalid_parameter.append(token)
+    return invalid_parameter, value
+
+def get_ttext(value):
+    """ttext = <matches _ttext_matcher>
+
+    We allow any non-TOKEN_ENDS in ttext, but add defects to the token's
+    defects list if we find non-ttext characters.  We also register defects for
+    *any* non-printables even though the RFC doesn't exclude all of them,
+    because we follow the spirit of RFC 5322.
+
+    """
+    m = _non_token_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected ttext but found '{}'".format(value))
+    ttext = m.group()
+    value = value[len(ttext):]
+    ttext = ValueTerminal(ttext, 'ttext')
+    _validate_xtext(ttext)
+    return ttext, value
+
+def get_token(value):
+    """token = [CFWS] 1*ttext [CFWS]
+
+    The RFC equivalent of ttext is any US-ASCII chars except space, ctls, or
+    tspecials.  We also exclude tabs even though the RFC doesn't.
+
+    The RFC implies the CFWS but is not explicit about it in the BNF.
+
+    """
+    mtoken = Token()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mtoken.append(token)
+    if value and value[0] in TOKEN_ENDS:
+        raise errors.HeaderParseError(
+            "expected token but found '{}'".format(value))
+    token, value = get_ttext(value)
+    mtoken.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mtoken.append(token)
+    return mtoken, value
+
+def get_attrtext(value):
+    """attrtext = 1*(any non-ATTRIBUTE_ENDS character)
+
+    We allow any non-ATTRIBUTE_ENDS in attrtext, but add defects to the
+    token's defects list if we find non-attrtext characters.  We also register
+    defects for *any* non-printables even though the RFC doesn't exclude all of
+    them, because we follow the spirit of RFC 5322.
+
+    """
+    m = _non_attribute_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected attrtext but found {!r}".format(value))
+    attrtext = m.group()
+    value = value[len(attrtext):]
+    attrtext = ValueTerminal(attrtext, 'attrtext')
+    _validate_xtext(attrtext)
+    return attrtext, value
+
+def get_attribute(value):
+    """ [CFWS] 1*attrtext [CFWS]
+
+    This version of the BNF makes the CFWS explicit, and as usual we use a
+    value terminal for the actual run of characters.  The RFC equivalent of
+    attrtext is the token characters, with the subtraction of '*', "'", and '%'.
+    We include tab in the excluded set just as we do for token.
+
+    """
+    attribute = Attribute()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    if value and value[0] in ATTRIBUTE_ENDS:
+        raise errors.HeaderParseError(
+            "expected token but found '{}'".format(value))
+    token, value = get_attrtext(value)
+    attribute.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    return attribute, value
+
+def get_extended_attrtext(value):
+    """attrtext = 1*(any non-ATTRIBUTE_ENDS character plus '%')
+
+    This is a special parsing routine so that we get a value that
+    includes % escapes as a single string (which we decode as a single
+    string later).
+
+    """
+    m = _non_extended_attribute_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected extended attrtext but found {!r}".format(value))
+    attrtext = m.group()
+    value = value[len(attrtext):]
+    attrtext = ValueTerminal(attrtext, 'extended-attrtext')
+    _validate_xtext(attrtext)
+    return attrtext, value
+
+def get_extended_attribute(value):
+    """ [CFWS] 1*extended_attrtext [CFWS]
+
+    This is like the non-extended version except we allow % characters, so that
+    we can pick up an encoded value as a single string.
+
+    """
+    # XXX: should we have an ExtendedAttribute TokenList?
+    attribute = Attribute()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    if value and value[0] in EXTENDED_ATTRIBUTE_ENDS:
+        raise errors.HeaderParseError(
+            "expected token but found '{}'".format(value))
+    token, value = get_extended_attrtext(value)
+    attribute.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    return attribute, value
+
+def get_section(value):
+    """ '*' digits
+
+    The formal BNF is more complicated because leading 0s are not allowed.  We
+    check for that and add a defect.  We also assume no CFWS is allowed between
+    the '*' and the digits, though the RFC is not crystal clear on that.
+    The caller should already have dealt with leading CFWS.
+
+    """
+    section = Section()
+    if not value or value[0] != '*':
+        raise errors.HeaderParseError("Expected section but found {}".format(
+                                        value))
+    section.append(ValueTerminal('*', 'section-marker'))
+    value = value[1:]
+    if not value or not value[0].isdigit():
+        raise errors.HeaderParseError("Expected section number but "
+                                      "found {}".format(value))
+    digits = ''
+    while value and value[0].isdigit():
+        digits += value[0]
+        value = value[1:]
+    if digits[0] == '0' and digits != '0':
+        section.defects.append(errors.InvalidHeaderError("section number"
+            "has an invalid leading 0"))
+    section.number = int(digits)
+    section.append(ValueTerminal(digits, 'digits'))
+    return section, value
+
+
+def get_value(value):
+    """ quoted-string / attribute
+
+    """
+    v = Value()
+    if not value:
+        raise errors.HeaderParseError("Expected value but found end of string")
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    if not value:
+        raise errors.HeaderParseError("Expected value but found "
+                                      "only {}".format(leader))
+    if value[0] == '"':
+        token, value = get_quoted_string(value)
+    else:
+        token, value = get_extended_attribute(value)
+    if leader is not None:
+        token[:0] = [leader]
+    v.append(token)
+    return v, value
+
+def get_parameter(value):
+    """ attribute [section] ["*"] [CFWS] "=" value
+
+    The CFWS is implied by the RFC but not made explicit in the BNF.  This
+    simplified form of the BNF from the RFC is made to conform with the RFC BNF
+    through some extra checks.  We do it this way because it makes both error
+    recovery and working with the resulting parse tree easier.
+    """
+    # It is possible CFWS would also be implicitly allowed between the section
+    # and the 'extended-attribute' marker (the '*') , but we've never seen that
+    # in the wild and we will therefore ignore the possibility.
+    param = Parameter()
+    token, value = get_attribute(value)
+    param.append(token)
+    if not value or value[0] == ';':
+        param.defects.append(errors.InvalidHeaderDefect("Parameter contains "
+            "name ({}) but no value".format(token)))
+        return param, value
+    if value[0] == '*':
+        try:
+            token, value = get_section(value)
+            param.sectioned = True
+            param.append(token)
+        except errors.HeaderParseError:
+            pass
+        if not value:
+            raise errors.HeaderParseError("Incomplete parameter")
+        if value[0] == '*':
+            param.append(ValueTerminal('*', 'extended-parameter-marker'))
+            value = value[1:]
+            param.extended = True
+    if value[0] != '=':
+        raise errors.HeaderParseError("Parameter not followed by '='")
+    param.append(ValueTerminal('=', 'parameter-separator'))
+    value = value[1:]
+    leader = None
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        param.append(token)
+    remainder = None
+    appendto = param
+    if param.extended and value and value[0] == '"':
+        # Now for some serious hackery to handle the common invalid case of
+        # double quotes around an extended value.  We also accept (with defect)
+        # a value marked as encoded that isn't really.
+        qstring, remainder = get_quoted_string(value)
+        inner_value = qstring.stripped_value
+        semi_valid = False
+        if param.section_number == 0:
+            if inner_value and inner_value[0] == "'":
+                semi_valid = True
+            else:
+                token, rest = get_attrtext(inner_value)
+                if rest and rest[0] == "'":
+                    semi_valid = True
+        else:
+            try:
+                token, rest = get_extended_attrtext(inner_value)
+            except:
+                pass
+            else:
+                if not rest:
+                    semi_valid = True
+        if semi_valid:
+            param.defects.append(errors.InvalidHeaderDefect(
+                "Quoted string value for extended parameter is invalid"))
+            param.append(qstring)
+            for t in qstring:
+                if t.token_type == 'bare-quoted-string':
+                    t[:] = []
+                    appendto = t
+                    break
+            value = inner_value
+        else:
+            remainder = None
+            param.defects.append(errors.InvalidHeaderDefect(
+                "Parameter marked as extended but appears to have a "
+                "quoted string value that is non-encoded"))
+    if value and value[0] == "'":
+        token = None
+    else:
+        token, value = get_value(value)
+    if not param.extended or param.section_number > 0:
+        if not value or value[0] != "'":
+            appendto.append(token)
+            if remainder is not None:
+                assert not value, value
+                value = remainder
+            return param, value
+        param.defects.append(errors.InvalidHeaderDefect(
+            "Apparent initial-extended-value but attribute "
+            "was not marked as extended or was not initial section"))
+    if not value:
+        # Assume the charset/lang is missing and the token is the value.
+        param.defects.append(errors.InvalidHeaderDefect(
+            "Missing required charset/lang delimiters"))
+        appendto.append(token)
+        if remainder is None:
+            return param, value
+    else:
+        if token is not None:
+            for t in token:
+                if t.token_type == 'extended-attrtext':
+                    break
+            t.token_type == 'attrtext'
+            appendto.append(t)
+            param.charset = t.value
+        if value[0] != "'":
+            raise errors.HeaderParseError("Expected RFC2231 char/lang encoding "
+                                          "delimiter, but found {!r}".format(value))
+        appendto.append(ValueTerminal("'", 'RFC2231-delimiter'))
+        value = value[1:]
+        if value and value[0] != "'":
+            token, value = get_attrtext(value)
+            appendto.append(token)
+            param.lang = token.value
+            if not value or value[0] != "'":
+                raise errors.HeaderParseError("Expected RFC2231 char/lang encoding "
+                                  "delimiter, but found {}".format(value))
+        appendto.append(ValueTerminal("'", 'RFC2231-delimiter'))
+        value = value[1:]
+    if remainder is not None:
+        # Treat the rest of value as bare quoted string content.
+        v = Value()
+        while value:
+            if value[0] in WSP:
+                token, value = get_fws(value)
+            else:
+                token, value = get_qcontent(value)
+            v.append(token)
+        token = v
+    else:
+        token, value = get_value(value)
+    appendto.append(token)
+    if remainder is not None:
+        assert not value, value
+        value = remainder
+    return param, value
+
+def parse_mime_parameters(value):
+    """ parameter *( ";" parameter )
+
+    That BNF is meant to indicate this routine should only be called after
+    finding and handling the leading ';'.  There is no corresponding rule in
+    the formal RFC grammar, but it is more convenient for us for the set of
+    parameters to be treated as its own TokenList.
+
+    This is 'parse' routine because it consumes the reminaing value, but it
+    would never be called to parse a full header.  Instead it is called to
+    parse everything after the non-parameter value of a specific MIME header.
+
+    """
+    mime_parameters = MimeParameters()
+    while value:
+        try:
+            token, value = get_parameter(value)
+            mime_parameters.append(token)
+        except errors.HeaderParseError as err:
+            leader = None
+            if value[0] in CFWS_LEADER:
+                leader, value = get_cfws(value)
+            if not value:
+                mime_parameters.append(leader)
+                return mime_parameters
+            if value[0] == ';':
+                if leader is not None:
+                    mime_parameters.append(leader)
+                mime_parameters.defects.append(errors.InvalidHeaderDefect(
+                    "parameter entry with no content"))
+            else:
+                token, value = get_invalid_parameter(value)
+                if leader:
+                    token[:0] = [leader]
+                mime_parameters.append(token)
+                mime_parameters.defects.append(errors.InvalidHeaderDefect(
+                    "invalid parameter {!r}".format(token)))
+        if value and value[0] != ';':
+            # Junk after the otherwise valid parameter.  Mark it as
+            # invalid, but it will have a value.
+            param = mime_parameters[-1]
+            param.token_type = 'invalid-parameter'
+            token, value = get_invalid_parameter(value)
+            param.extend(token)
+            mime_parameters.defects.append(errors.InvalidHeaderDefect(
+                "parameter with invalid trailing text {!r}".format(token)))
+        if value:
+            # Must be a ';' at this point.
+            mime_parameters.append(ValueTerminal(';', 'parameter-separator'))
+            value = value[1:]
+    return mime_parameters
+
+def _find_mime_parameters(tokenlist, value):
+    """Do our best to find the parameters in an invalid MIME header
+
+    """
+    while value and value[0] != ';':
+        if value[0] in PHRASE_ENDS:
+            tokenlist.append(ValueTerminal(value[0], 'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            tokenlist.append(token)
+    if not value:
+        return
+    tokenlist.append(ValueTerminal(';', 'parameter-separator'))
+    tokenlist.append(parse_mime_parameters(value[1:]))
+
+def parse_content_type_header(value):
+    """ maintype "/" subtype *( ";" parameter )
+
+    The maintype and substype are tokens.  Theoretically they could
+    be checked against the official IANA list + x-token, but we
+    don't do that.
+    """
+    ctype = ContentType()
+    recover = False
+    if not value:
+        ctype.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing content type specification"))
+        return ctype
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Expected content maintype but found {!r}".format(value)))
+        _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.append(token)
+    # XXX: If we really want to follow the formal grammar we should make
+    # mantype and subtype specialized TokenLists here.  Probably not worth it.
+    if not value or value[0] != '/':
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Invalid content type"))
+        if value:
+            _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.maintype = token.value.strip().lower()
+    ctype.append(ValueTerminal('/', 'content-type-separator'))
+    value = value[1:]
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Expected content subtype but found {!r}".format(value)))
+        _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.append(token)
+    ctype.subtype = token.value.strip().lower()
+    if not value:
+        return ctype
+    if value[0] != ';':
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Only parameters are valid after content type, but "
+            "found {!r}".format(value)))
+        # The RFC requires that a syntactically invalid content-type be treated
+        # as text/plain.  Perhaps we should postel this, but we should probably
+        # only do that if we were checking the subtype value against IANA.
+        del ctype.maintype, ctype.subtype
+        _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.append(ValueTerminal(';', 'parameter-separator'))
+    ctype.append(parse_mime_parameters(value[1:]))
+    return ctype
+
+def parse_content_disposition_header(value):
+    """ disposition-type *( ";" parameter )
+
+    """
+    disp_header = ContentDisposition()
+    if not value:
+        disp_header.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing content disposition"))
+        return disp_header
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        disp_header.defects.append(errors.InvalidHeaderDefect(
+            "Expected content disposition but found {!r}".format(value)))
+        _find_mime_parameters(disp_header, value)
+        return disp_header
+    disp_header.append(token)
+    disp_header.content_disposition = token.value.strip().lower()
+    if not value:
+        return disp_header
+    if value[0] != ';':
+        disp_header.defects.append(errors.InvalidHeaderDefect(
+            "Only parameters are valid after content disposition, but "
+            "found {!r}".format(value)))
+        _find_mime_parameters(disp_header, value)
+        return disp_header
+    disp_header.append(ValueTerminal(';', 'parameter-separator'))
+    disp_header.append(parse_mime_parameters(value[1:]))
+    return disp_header
+
+def parse_content_transfer_encoding_header(value):
+    """ mechanism
+
+    """
+    # We should probably validate the values, since the list is fixed.
+    cte_header = ContentTransferEncoding()
+    if not value:
+        cte_header.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing content transfer encoding"))
+        return cte_header
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        cte_header.defects.append(errors.InvalidHeaderDefect(
+            "Expected content transfer encoding but found {!r}".format(value)))
+    else:
+        cte_header.append(token)
+        cte_header.cte = token.value.strip().lower()
+    if not value:
+        return cte_header
+    while value:
+        cte_header.defects.append(errors.InvalidHeaderDefect(
+            "Extra text after content transfer encoding"))
+        if value[0] in PHRASE_ENDS:
+            cte_header.append(ValueTerminal(value[0], 'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            cte_header.append(token)
+    return cte_header
+
+
+#
+# Header folding
+#
+# Header folding is complex, with lots of rules and corner cases.  The
+# following code does its best to obey the rules and handle the corner
+# cases, but you can be sure there are few bugs:)
+#
+# This folder generally canonicalizes as it goes, preferring the stringified
+# version of each token.  The tokens contain information that supports the
+# folder, including which tokens can be encoded in which ways.
+#
+# Folded text is accumulated in a simple list of strings ('lines'), each
+# one of which should be less than policy.max_line_length ('maxlen').
+#
+
+def _steal_trailing_WSP_if_exists(lines):
+    wsp = ''
+    if lines and lines[-1] and lines[-1][-1] in WSP:
+        wsp = lines[-1][-1]
+        lines[-1] = lines[-1][:-1]
+    return wsp
+
+def _refold_parse_tree(parse_tree, *, policy):
+    """Return string of contents of parse_tree folded according to RFC rules.
+
+    """
+    # max_line_length 0/None means no limit, ie: infinitely long.
+    maxlen = policy.max_line_length or float("+inf")
+    encoding = 'utf-8' if policy.utf8 else 'us-ascii'
+    lines = ['']
+    last_ew = None
+    wrap_as_ew_blocked = 0
+    want_encoding = False
+    end_ew_not_allowed = Terminal('', 'wrap_as_ew_blocked')
+    parts = list(parse_tree)
+    while parts:
+        part = parts.pop(0)
+        if part is end_ew_not_allowed:
+            wrap_as_ew_blocked -= 1
+            continue
+        tstr = str(part)
+        try:
+            tstr.encode(encoding)
+            charset = encoding
+        except UnicodeEncodeError:
+            if any(isinstance(x, errors.UndecodableBytesDefect)
+                   for x in part.all_defects):
+                charset = 'unknown-8bit'
+            else:
+                # If policy.utf8 is false this should really be taken from a
+                # 'charset' property on the policy.
+                charset = 'utf-8'
+            want_encoding = True
+        if part.token_type == 'mime-parameters':
+            # Mime parameter folding (using RFC2231) is extra special.
+            _fold_mime_parameters(part, lines, maxlen, encoding)
+            continue
+        if want_encoding and not wrap_as_ew_blocked:
+            if not part.as_ew_allowed:
+                want_encoding = False
+                last_ew = None
+                if part.syntactic_break:
+                    encoded_part = part.fold(policy=policy)[:-1] # strip nl
+                    if policy.linesep not in encoded_part:
+                        # It fits on a single line
+                        if len(encoded_part) > maxlen - len(lines[-1]):
+                            # But not on this one, so start a new one.
+                            newline = _steal_trailing_WSP_if_exists(lines)
+                            # XXX what if encoded_part has no leading FWS?
+                            lines.append(newline)
+                        lines[-1] += encoded_part
+                        continue
+                # Either this is not a major syntactic break, so we don't
+                # want it on a line by itself even if it fits, or it
+                # doesn't fit on a line by itself.  Either way, fall through
+                # to unpacking the subparts and wrapping them.
+            if not hasattr(part, 'encode'):
+                # It's not a Terminal, do each piece individually.
+                parts = list(part) + parts
+            else:
+                # It's a terminal, wrap it as an encoded word, possibly
+                # combining it with previously encoded words if allowed.
+                last_ew = _fold_as_ew(tstr, lines, maxlen, last_ew,
+                                      part.ew_combine_allowed, charset)
+            want_encoding = False
+            continue
+        if len(tstr) <= maxlen - len(lines[-1]):
+            lines[-1] += tstr
+            continue
+        # This part is too long to fit.  The RFC wants us to break at
+        # "major syntactic breaks", so unless we don't consider this
+        # to be one, check if it will fit on the next line by itself.
+        if (part.syntactic_break and
+                len(tstr) + 1 <= maxlen):
+            newline = _steal_trailing_WSP_if_exists(lines)
+            if newline or part.startswith_fws():
+                lines.append(newline + tstr)
+                continue
+        if not hasattr(part, 'encode'):
+            # It's not a terminal, try folding the subparts.
+            newparts = list(part)
+            if not part.as_ew_allowed:
+                wrap_as_ew_blocked += 1
+                newparts.append(end_ew_not_allowed)
+            parts = newparts + parts
+            continue
+        if part.as_ew_allowed and not wrap_as_ew_blocked:
+            # It doesn't need CTE encoding, but encode it anyway so we can
+            # wrap it.
+            parts.insert(0, part)
+            want_encoding = True
+            continue
+        # We can't figure out how to wrap, it, so give up.
+        newline = _steal_trailing_WSP_if_exists(lines)
+        if newline or part.startswith_fws():
+            lines.append(newline + tstr)
+        else:
+            # We can't fold it onto the next line either...
+            lines[-1] += tstr
+    return policy.linesep.join(lines) + policy.linesep
+
+def _fold_as_ew(to_encode, lines, maxlen, last_ew, ew_combine_allowed, charset):
+    """Fold string to_encode into lines as encoded word, combining if allowed.
+    Return the new value for last_ew, or None if ew_combine_allowed is False.
+
+    If there is already an encoded word in the last line of lines (indicated by
+    a non-None value for last_ew) and ew_combine_allowed is true, decode the
+    existing ew, combine it with to_encode, and re-encode.  Otherwise, encode
+    to_encode.  In either case, split to_encode as necessary so that the
+    encoded segments fit within maxlen.
+
+    """
+    if last_ew is not None and ew_combine_allowed:
+        to_encode = str(
+            get_unstructured(lines[-1][last_ew:] + to_encode))
+        lines[-1] = lines[-1][:last_ew]
+    if to_encode[0] in WSP:
+        # We're joining this to non-encoded text, so don't encode
+        # the leading blank.
+        leading_wsp = to_encode[0]
+        to_encode = to_encode[1:]
+        if (len(lines[-1]) == maxlen):
+            lines.append(_steal_trailing_WSP_if_exists(lines))
+        lines[-1] += leading_wsp
+    trailing_wsp = ''
+    if to_encode[-1] in WSP:
+        # Likewise for the trailing space.
+        trailing_wsp = to_encode[-1]
+        to_encode = to_encode[:-1]
+    new_last_ew = len(lines[-1]) if last_ew is None else last_ew
+    while to_encode:
+        remaining_space = maxlen - len(lines[-1])
+        # The RFC2047 chrome takes up 7 characters plus the length
+        # of the charset name.
+        encode_as = 'utf-8' if charset == 'us-ascii' else charset
+        text_space = remaining_space - len(encode_as) - 7
+        if text_space <= 0:
+            lines.append(' ')
+            # XXX We'll get an infinite loop here if maxlen is <= 7
+            continue
+        first_part = to_encode[:text_space]
+        ew = _ew.encode(first_part, charset=encode_as)
+        excess = len(ew) - remaining_space
+        if excess > 0:
+            # encode always chooses the shortest encoding, so this
+            # is guaranteed to fit at this point.
+            first_part = first_part[:-excess]
+            ew = _ew.encode(first_part)
+        lines[-1] += ew
+        to_encode = to_encode[len(first_part):]
+        if to_encode:
+            lines.append(' ')
+            new_last_ew = len(lines[-1])
+    lines[-1] += trailing_wsp
+    return new_last_ew if ew_combine_allowed else None
+
+def _fold_mime_parameters(part, lines, maxlen, encoding):
+    """Fold TokenList 'part' into the 'lines' list as mime parameters.
+
+    Using the decoded list of parameters and values, format them according to
+    the RFC rules, including using RFC2231 encoding if the value cannot be
+    expressed in 'encoding' and/or the parameter+value is too long to fit
+    within 'maxlen'.
+
+    """
+    # Special case for RFC2231 encoding: start from decoded values and use
+    # RFC2231 encoding iff needed.
+    #
+    # Note that the 1 and 2s being added to the length calculations are
+    # accounting for the possibly-needed spaces and semicolons we'll be adding.
+    #
+    for name, value in part.params:
+        # XXX What if this ';' puts us over maxlen the first time through the
+        # loop?  We should split the header value onto a newline in that case,
+        # but to do that we need to recognize the need earlier or reparse the
+        # header, so I'm going to ignore that bug for now.  It'll only put us
+        # one character over.
+        if not lines[-1].rstrip().endswith(';'):
+            lines[-1] += ';'
+        charset = encoding
+        error_handler = 'strict'
+        try:
+            value.encode(encoding)
+            encoding_required = False
+        except UnicodeEncodeError:
+            encoding_required = True
+            if utils._has_surrogates(value):
+                charset = 'unknown-8bit'
+                error_handler = 'surrogateescape'
+            else:
+                charset = 'utf-8'
+        if encoding_required:
+            encoded_value = parse.quote(
+                value, safe='', errors=error_handler)
+            tstr = "{}*={}''{}".format(name, charset, encoded_value)
+        else:
+            tstr = '{}={}'.format(name, quote_string(value))
+        if len(lines[-1]) + len(tstr) + 1 < maxlen:
+            lines[-1] = lines[-1] + ' ' + tstr
+            continue
+        elif len(tstr) + 2 <= maxlen:
+            lines.append(' ' + tstr)
+            continue
+        # We need multiple sections.  We are allowed to mix encoded and
+        # non-encoded sections, but we aren't going to.  We'll encode them all.
+        section = 0
+        extra_chrome = charset + "''"
+        while value:
+            chrome_len = len(name) + len(str(section)) + 3 + len(extra_chrome)
+            if maxlen <= chrome_len + 3:
+                # We need room for the leading blank, the trailing semicolon,
+                # and at least one character of the value.  If we don't
+                # have that, we'd be stuck, so in that case fall back to
+                # the RFC standard width.
+                maxlen = 78
+            splitpoint = maxchars = maxlen - chrome_len - 2
+            while True:
+                partial = value[:splitpoint]
+                encoded_value = parse.quote(
+                    partial, safe='', errors=error_handler)
+                if len(encoded_value) <= maxchars:
+                    break
+                splitpoint -= 1
+            lines.append(" {}*{}*={}{}".format(
+                name, section, extra_chrome, encoded_value))
+            extra_chrome = ''
+            section += 1
+            value = value[splitpoint:]
+            if value:
+                lines[-1] += ';'
diff --git a/modules/language/python/module/email/_policybase.py b/modules/language/python/module/email/_policybase.py
index a8633e2..bbc8b3c 100644
--- a/modules/language/python/module/email/_policybase.py
+++ b/modules/language/python/module/email/_policybase.py
@@ -3,7 +3,6 @@ module(email,_policybase)
 
 Allows fine grained feature control of how the package parses and emits data.
 """
-
 import abc
 import email.header as header
 import email.charset as _charset
@@ -13,6 +12,7 @@ __all__ = [
     'Policy',
     'Compat32',
     'compat32',
+    '_extend_docstrings'
     ]
 
 
@@ -101,9 +101,9 @@ def _extend_docstrings(cls):
     if cls.__doc__ and cls.__doc__.startswith('+'):
         cls.__doc__ = _append_doc(cls.__bases__[0].__doc__, cls.__doc__)
     for name, attr in cls.__dict__.items():
-        if attr.__doc__ and attr.__doc__.startswith('+'):
+        if getattr(attr, '__doc__',False) and attr.__doc__.startswith('+'):
             for c in (c for base in cls.__bases__ for c in base.mro()):
-                doc = getattr(getattr(c, name), '__doc__')
+                doc = getattr(getattr(c, name, False), '__doc__', False)
                 if doc:
                     attr.__doc__ = _append_doc(doc, attr.__doc__)
                     break
diff --git a/modules/language/python/module/email/contentmanager.py b/modules/language/python/module/email/contentmanager.py
new file mode 100644
index 0000000..5eaf2ee
--- /dev/null
+++ b/modules/language/python/module/email/contentmanager.py
@@ -0,0 +1,254 @@
+module(email,contentmanager)
+
+__all__=['ContentManager','raw_data_manager']
+
+import binascii
+import email.charset as charset
+import email.message as message
+import email.errors as errors
+import email.quoprimime as quoprimime
+
+class ContentManager:
+
+    def __init__(self):
+        self.get_handlers = {}
+        self.set_handlers = {}
+
+    def add_get_handler(self, key, handler):
+        self.get_handlers[key] = handler
+
+    def get_content(self, msg, *args, **kw):
+        content_type = msg.get_content_type()
+        if content_type in self.get_handlers:
+            return self.get_handlers[content_type](msg, *args, **kw)
+        maintype = msg.get_content_maintype()
+        if maintype in self.get_handlers:
+            return self.get_handlers[maintype](msg, *args, **kw)
+        if '' in self.get_handlers:
+            return self.get_handlers[''](msg, *args, **kw)
+        raise KeyError(content_type)
+
+    def add_set_handler(self, typekey, handler):
+        self.set_handlers[typekey] = handler
+
+    def set_content(self, msg, obj, *args, **kw):
+        if msg.get_content_maintype() == 'multipart':
+            # XXX: is this error a good idea or not?  We can remove it later,
+            # but we can't add it later, so do it for now.
+            raise TypeError("set_content not valid on multipart")
+        handler = self._find_set_handler(msg, obj)
+        msg.clear_content()
+        handler(msg, obj, *args, **kw)
+
+    def _find_set_handler(self, msg, obj):
+        full_path_for_error = None
+        for typ in type(obj).__mro__:
+            if typ in self.set_handlers:
+                return self.set_handlers[typ]
+            qname = typ.__qualname__
+            modname = getattr(typ, '__module__', '')
+            full_path = '.'.join((modname, qname)) if modname else qname
+            if full_path_for_error is None:
+                full_path_for_error = full_path
+            if full_path in self.set_handlers:
+                return self.set_handlers[full_path]
+            if qname in self.set_handlers:
+                return self.set_handlers[qname]
+            name = typ.__name__
+            if name in self.set_handlers:
+                return self.set_handlers[name]
+        if None in self.set_handlers:
+            return self.set_handlers[None]
+        raise KeyError(full_path_for_error)
+
+
+raw_data_manager = ContentManager()
+
+
+def get_text_content(msg, errors='replace'):
+    content = msg.get_payload(decode=True)
+    charset = msg.get_param('charset', 'ASCII')
+    return content.decode(charset, errors=errors)
+raw_data_manager.add_get_handler('text', get_text_content)
+
+
+def get_non_text_content(msg):
+    return msg.get_payload(decode=True)
+for maintype in 'audio image video application'.split():
+    raw_data_manager.add_get_handler(maintype, get_non_text_content)
+
+
+def get_message_content(msg):
+    return msg.get_payload(0)
+for subtype in 'rfc822 external-body'.split():
+    raw_data_manager.add_get_handler('message/'+subtype, get_message_content)
+
+
+def get_and_fixup_unknown_message_content(msg):
+    # If we don't understand a message subtype, we are supposed to treat it as
+    # if it were application/octet-stream, per
+    # tools.ietf.org/html/rfc2046#section-5.2.4.  Feedparser doesn't do that,
+    # so do our best to fix things up.  Note that it is *not* appropriate to
+    # model message/partial content as Message objects, so they are handled
+    # here as well.  (How to reassemble them is out of scope for this comment :)
+    return bytes(msg.get_payload(0))
+raw_data_manager.add_get_handler('message',
+                                 get_and_fixup_unknown_message_content)
+
+
+def _prepare_set(msg, maintype, subtype, headers):
+    msg['Content-Type'] = '/'.join((maintype, subtype))
+    if headers:
+        if not hasattr(headers[0], 'name'):
+            mp = msg.policy
+            headers = [mp.header_factory(*mp.header_source_parse([header]))
+                       for header in headers]
+        try:
+            for header in headers:
+                if header.defects:
+                    raise header.defects[0]
+                msg[header.name] = header
+        except errors.HeaderDefect as exc:
+            raise ValueError("Invalid header: {}".format(
+                                header.fold(policy=msg.policy))) from exc
+
+
+def _finalize_set(msg, disposition, filename, cid, params):
+    if disposition is None and filename is not None:
+        disposition = 'attachment'
+    if disposition is not None:
+        msg['Content-Disposition'] = disposition
+    if filename is not None:
+        msg.set_param('filename',
+                      filename,
+                      header='Content-Disposition',
+                      replace=True)
+    if cid is not None:
+        msg['Content-ID'] = cid
+    if params is not None:
+        for key, value in params.items():
+            msg.set_param(key, value)
+
+
+# XXX: This is a cleaned-up version of base64mime.body_encode (including a bug
+# fix in the calculation of unencoded_bytes_per_line).  It would be nice to
+# drop both this and quoprimime.body_encode in favor of enhanced binascii
+# routines that accepted a max_line_length parameter.
+def _encode_base64(data, max_line_length):
+    encoded_lines = []
+    unencoded_bytes_per_line = max_line_length // 4 * 3
+    for i in range(0, len(data), unencoded_bytes_per_line):
+        thisline = data[i:i+unencoded_bytes_per_line]
+        encoded_lines.append(binascii.b2a_base64(thisline).decode('ascii'))
+    return ''.join(encoded_lines)
+
+
+def _encode_text(string, charset, cte, policy):
+    lines = string.encode(charset).splitlines()
+    linesep = policy.linesep.encode('ascii')
+    def embedded_body(lines): return linesep.join(lines) + linesep
+    def normal_body(lines): return b'\n'.join(lines) + b'\n'
+    if cte==None:
+        # Use heuristics to decide on the "best" encoding.
+        try:
+            return '7bit', normal_body(lines).decode('ascii')
+        except UnicodeDecodeError:
+            pass
+        if (policy.cte_type == '8bit' and
+                max(len(x) for x in lines) <= policy.max_line_length):
+            return '8bit', normal_body(lines).decode('ascii', 'surrogateescape')
+        sniff = embedded_body(lines[:10])
+        sniff_qp = quoprimime.body_encode(sniff.decode('latin-1'),
+                                          policy.max_line_length)
+        sniff_base64 = binascii.b2a_base64(sniff)
+        # This is a little unfair to qp; it includes lineseps, base64 doesn't.
+        if len(sniff_qp) > len(sniff_base64):
+            cte = 'base64'
+        else:
+            cte = 'quoted-printable'
+            if len(lines) <= 10:
+                return cte, sniff_qp
+    if cte == '7bit':
+        data = normal_body(lines).decode('ascii')
+    elif cte == '8bit':
+        data = normal_body(lines).decode('ascii', 'surrogateescape')
+    elif cte == 'quoted-printable':
+        data = quoprimime.body_encode(normal_body(lines).decode('latin-1'),
+                                      policy.max_line_length)
+    elif cte == 'base64':
+        data = _encode_base64(embedded_body(lines), policy.max_line_length)
+    else:
+        raise ValueError("Unknown content transfer encoding {}".format(cte))
+    return cte, data
+
+
+def set_text_content(msg, string, subtype="plain", charset='utf-8', cte=None,
+                     disposition=None, filename=None, cid=None,
+                     params=None, headers=None):
+    _prepare_set(msg, 'text', subtype, headers)
+    cte, payload = _encode_text(string, charset, cte, msg.policy)
+    msg.set_payload(payload)
+    msg.set_param('charset',
+                  charset.ALIASES.get(charset, charset),
+                  replace=True)
+    msg['Content-Transfer-Encoding'] = cte
+    _finalize_set(msg, disposition, filename, cid, params)
+raw_data_manager.add_set_handler(str, set_text_content)
+
+
+def set_message_content(msg, message, subtype="rfc822", cte=None,
+                       disposition=None, filename=None, cid=None,
+                       params=None, headers=None):
+    if subtype == 'partial':
+        raise ValueError("message/partial is not supported for Message objects")
+    if subtype == 'rfc822':
+        if cte not in (None, '7bit', '8bit', 'binary'):
+            # http://tools.ietf.org/html/rfc2046#section-5.2.1 mandate.
+            raise ValueError(
+                "message/rfc822 parts do not support cte={}".format(cte))
+        # 8bit will get coerced on serialization if policy.cte_type='7bit'.  We
+        # may end up claiming 8bit when it isn't needed, but the only negative
+        # result of that should be a gateway that needs to coerce to 7bit
+        # having to look through the whole embedded message to discover whether
+        # or not it actually has to do anything.
+        cte = '8bit' if cte is None else cte
+    elif subtype == 'external-body':
+        if cte not in (None, '7bit'):
+            # http://tools.ietf.org/html/rfc2046#section-5.2.3 mandate.
+            raise ValueError(
+                "message/external-body parts do not support cte={}".format(cte))
+        cte = '7bit'
+    elif cte is None:
+        # http://tools.ietf.org/html/rfc2046#section-5.2.4 says all future
+        # subtypes should be restricted to 7bit, so assume that.
+        cte = '7bit'
+    _prepare_set(msg, 'message', subtype, headers)
+    msg.set_payload([message])
+    msg['Content-Transfer-Encoding'] = cte
+    _finalize_set(msg, disposition, filename, cid, params)
+raw_data_manager.add_set_handler(message.Message, set_message_content)
+
+
+def set_bytes_content(msg, data, maintype, subtype, cte='base64',
+                     disposition=None, filename=None, cid=None,
+                     params=None, headers=None):
+    _prepare_set(msg, maintype, subtype, headers)
+    if cte == 'base64':
+        data = _encode_base64(data, max_line_length=msg.policy.max_line_length)
+    elif cte == 'quoted-printable':
+        # XXX: quoprimime.body_encode won't encode newline characters in data,
+        # so we can't use it.  This means max_line_length is ignored.  Another
+        # bug to fix later.  (Note: encoders.quopri is broken on line ends.)
+        data = binascii.b2a_qp(data, istext=False, header=False, quotetabs=True)
+        data = data.decode('ascii')
+    elif cte == '7bit':
+        # Make sure it really is only ASCII.  The early warning here seems
+        # worth the overhead...if you care write your own content manager :).
+        data.encode('ascii')
+    elif cte in ('8bit', 'binary'):
+        data = data.decode('ascii', 'surrogateescape')
+    msg.set_payload(data)
+    msg['Content-Transfer-Encoding'] = cte
+    _finalize_set(msg, disposition, filename, cid, params)
+for typ in (bytes, bytearray, memoryview):
+    raw_data_manager.add_set_handler(typ, set_bytes_content)
diff --git a/modules/language/python/module/email/feedparser.py b/modules/language/python/module/email/feedparser.py
index f07448a..2f31633 100644
--- a/modules/language/python/module/email/feedparser.py
+++ b/modules/language/python/module/email/feedparser.py
@@ -23,7 +23,6 @@ object's .defects attribute.
 __all__ = ['FeedParser', 'BytesFeedParser']
 
 import re
-
 import email.errors as errors
 from email._policybase import compat32
 from collections import deque
diff --git a/modules/language/python/module/email/generator.py b/modules/language/python/module/email/generator.py
new file mode 100644
index 0000000..2b90fe5
--- /dev/null
+++ b/modules/language/python/module/email/generator.py
@@ -0,0 +1,509 @@
+module(email,generator)
+# Copyright (C) 2001-2010 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Classes to generate plain text from a message object tree."""
+
+__all__ = ['Generator', 'DecodedGenerator', 'BytesGenerator']
+
+import re
+import sys
+import time
+import random
+
+from copy import deepcopy
+from io import StringIO, BytesIO
+from email.utils import _has_surrogates
+
+UNDERSCORE = '_'
+NL = '\n'  # XXX: no longer used by the code below.
+
+NLCRE = re.compile(r'\r\n|\r|\n')
+fcre = re.compile(r'^From ', re.MULTILINE)
+
+
+
+class Generator:
+    """Generates output from a Message object tree.
+
+    This basic generator writes the message to the given file object as plain
+    text.
+    """
+    #
+    # Public interface
+    #
+
+    def __init__(self, outfp, mangle_from_=None, maxheaderlen=None, *,
+                 policy=None):
+        """Create the generator for message flattening.
+
+        outfp is the output file-like object for writing the message to.  It
+        must have a write() method.
+
+        Optional mangle_from_ is a flag that, when True (the default if policy
+        is not set), escapes From_ lines in the body of the message by putting
+        a `>' in front of them.
+
+        Optional maxheaderlen specifies the longest length for a non-continued
+        header.  When a header line is longer (in characters, with tabs
+        expanded to 8 spaces) than maxheaderlen, the header will split as
+        defined in the Header class.  Set maxheaderlen to zero to disable
+        header wrapping.  The default is 78, as recommended (but not required)
+        by RFC 2822.
+
+        The policy keyword specifies a policy object that controls a number of
+        aspects of the generator's operation.  If no policy is specified,
+        the policy associated with the Message object passed to the
+        flatten method is used.
+
+        """
+
+        if mangle_from_ is None:
+            mangle_from_ = True if policy is None else policy.mangle_from_
+        self._fp = outfp
+        self._mangle_from_ = mangle_from_
+        self.maxheaderlen = maxheaderlen
+        self.policy = policy
+
+    def write(self, s):
+        # Just delegate to the file object
+        self._fp.write(s)
+
+    def flatten(self, msg, unixfrom=False, linesep=None):
+        r"""Print the message object tree rooted at msg to the output file
+        specified when the Generator instance was created.
+
+        unixfrom is a flag that forces the printing of a Unix From_ delimiter
+        before the first object in the message tree.  If the original message
+        has no From_ delimiter, a `standard' one is crafted.  By default, this
+        is False to inhibit the printing of any From_ delimiter.
+
+        Note that for subobjects, no From_ line is printed.
+
+        linesep specifies the characters used to indicate a new line in
+        the output.  The default value is determined by the policy specified
+        when the Generator instance was created or, if none was specified,
+        from the policy associated with the msg.
+
+        """
+        # We use the _XXX constants for operating on data that comes directly
+        # from the msg, and _encoded_XXX constants for operating on data that
+        # has already been converted (to bytes in the BytesGenerator) and
+        # inserted into a temporary buffer.
+        policy = msg.policy if self.policy is None else self.policy
+        if linesep is not None:
+            policy = policy.clone(linesep=linesep)
+        if self.maxheaderlen is not None:
+            policy = policy.clone(max_line_length=self.maxheaderlen)
+        self._NL = policy.linesep
+        self._encoded_NL = self._encode(self._NL)
+        self._EMPTY = ''
+        self._encoded_EMPTY = self._encode(self._EMPTY)
+        # Because we use clone (below) when we recursively process message
+        # subparts, and because clone uses the computed policy (not None),
+        # submessages will automatically get set to the computed policy when
+        # they are processed by this code.
+        old_gen_policy = self.policy
+        old_msg_policy = msg.policy
+        try:
+            self.policy = policy
+            msg.policy = policy
+            if unixfrom:
+                ufrom = msg.get_unixfrom()
+                if not ufrom:
+                    ufrom = 'From nobody ' + time.ctime(time.time())
+                self.write(ufrom + self._NL)
+            self._write(msg)
+        finally:
+            self.policy = old_gen_policy
+            msg.policy = old_msg_policy
+
+    def clone(self, fp):
+        """Clone this generator with the exact same options."""
+        return self.__class__(fp,
+                              self._mangle_from_,
+                              None, # Use policy setting, which we've adjusted
+                              policy=self.policy)
+
+    #
+    # Protected interface - undocumented ;/
+    #
+
+    # Note that we use 'self.write' when what we are writing is coming from
+    # the source, and self._fp.write when what we are writing is coming from a
+    # buffer (because the Bytes subclass has already had a chance to transform
+    # the data in its write method in that case).  This is an entirely
+    # pragmatic split determined by experiment; we could be more general by
+    # always using write and having the Bytes subclass write method detect when
+    # it has already transformed the input; but, since this whole thing is a
+    # hack anyway this seems good enough.
+
+    def _new_buffer(self):
+        # BytesGenerator overrides this to return BytesIO.
+        return StringIO()
+
+    def _encode(self, s):
+        # BytesGenerator overrides this to encode strings to bytes.
+        return s
+
+    def _write_lines(self, lines):
+        # We have to transform the line endings.
+        if not lines:
+            return
+        lines = NLCRE.split(lines)
+        for line in lines[:-1]:
+            self.write(line)
+            self.write(self._NL)
+        if lines[-1]:
+            self.write(lines[-1])
+        # XXX logic tells me this else should be needed, but the tests fail
+        # with it and pass without it.  (NLCRE.split ends with a blank element
+        # if and only if there was a trailing newline.)
+        #else:
+        #    self.write(self._NL)
+
+    def _write(self, msg):
+        # We can't write the headers yet because of the following scenario:
+        # say a multipart message includes the boundary string somewhere in
+        # its body.  We'd have to calculate the new boundary /before/ we write
+        # the headers so that we can write the correct Content-Type:
+        # parameter.
+        #
+        # The way we do this, so as to make the _handle_*() methods simpler,
+        # is to cache any subpart writes into a buffer.  The we write the
+        # headers and the buffer contents.  That way, subpart handlers can
+        # Do The Right Thing, and can still modify the Content-Type: header if
+        # necessary.
+        oldfp = self._fp
+        try:
+            self._munge_cte = None
+            self._fp = sfp = self._new_buffer()
+            self._dispatch(msg)
+        finally:
+            self._fp = oldfp
+            munge_cte = self._munge_cte
+            del self._munge_cte
+        # If we munged the cte, copy the message again and re-fix the CTE.
+        if munge_cte:
+            msg = deepcopy(msg)
+            msg.replace_header('content-transfer-encoding', munge_cte[0])
+            msg.replace_header('content-type', munge_cte[1])
+        # Write the headers.  First we see if the message object wants to
+        # handle that itself.  If not, we'll do it generically.
+        meth = getattr(msg, '_write_headers', None)
+        if meth is None:
+            self._write_headers(msg)
+        else:
+            meth(self)
+        self._fp.write(sfp.getvalue())
+
+    def _dispatch(self, msg):
+        # Get the Content-Type: for the message, then try to dispatch to
+        # self._handle_<maintype>_<subtype>().  If there's no handler for the
+        # full MIME type, then dispatch to self._handle_<maintype>().  If
+        # that's missing too, then dispatch to self._writeBody().
+        main = msg.get_content_maintype()
+        sub = msg.get_content_subtype()
+        specific = UNDERSCORE.join((main, sub)).replace('-', '_')
+        meth = getattr(self, '_handle_' + specific, None)
+        if meth is None:
+            generic = main.replace('-', '_')
+            meth = getattr(self, '_handle_' + generic, None)
+            if meth is None:
+                meth = self._writeBody
+        meth(msg)
+
+    #
+    # Default handlers
+    #
+
+    def _write_headers(self, msg):
+        for h, v in msg.raw_items():
+            self.write(self.policy.fold(h, v))
+        # A blank line always separates headers from body
+        self.write(self._NL)
+
+    #
+    # Handlers for writing types and subtypes
+    #
+
+    def _handle_text(self, msg):
+        payload = msg.get_payload()
+        if payload is None:
+            return
+        if not isinstance(payload, str):
+            raise TypeError('string payload expected: %s' % type(payload))
+        if _has_surrogates(msg._payload):
+            charset = msg.get_param('charset')
+            if charset is not None:
+                # XXX: This copy stuff is an ugly hack to avoid modifying the
+                # existing message.
+                msg = deepcopy(msg)
+                del msg['content-transfer-encoding']
+                msg.set_payload(payload, charset)
+                payload = msg.get_payload()
+                self._munge_cte = (msg['content-transfer-encoding'],
+                                   msg['content-type'])
+        if self._mangle_from_:
+            payload = fcre.sub('>From ', payload)
+        self._write_lines(payload)
+
+    # Default body handler
+    _writeBody = _handle_text
+
+    def _handle_multipart(self, msg):
+        # The trick here is to write out each part separately, merge them all
+        # together, and then make sure that the boundary we've chosen isn't
+        # present in the payload.
+        msgtexts = []
+        subparts = msg.get_payload()
+        if subparts is None:
+            subparts = []
+        elif isinstance(subparts, str):
+            # e.g. a non-strict parse of a message with no starting boundary.
+            self.write(subparts)
+            return
+        elif not isinstance(subparts, list):
+            # Scalar payload
+            subparts = [subparts]
+        for part in subparts:
+            s = self._new_buffer()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False, linesep=self._NL)
+            msgtexts.append(s.getvalue())
+        # BAW: What about boundaries that are wrapped in double-quotes?
+        boundary = msg.get_boundary()
+        if not boundary:
+            # Create a boundary that doesn't appear in any of the
+            # message texts.
+            alltext = self._encoded_NL.join(msgtexts)
+            boundary = self._make_boundary(alltext)
+            msg.set_boundary(boundary)
+        # If there's a preamble, write it out, with a trailing CRLF
+        if msg.preamble is not None:
+            if self._mangle_from_:
+                preamble = fcre.sub('>From ', msg.preamble)
+            else:
+                preamble = msg.preamble
+            self._write_lines(preamble)
+            self.write(self._NL)
+        # dash-boundary transport-padding CRLF
+        self.write('--' + boundary + self._NL)
+        # body-part
+        if msgtexts:
+            self._fp.write(msgtexts.pop(0))
+        # *encapsulation
+        # --> delimiter transport-padding
+        # --> CRLF body-part
+        for body_part in msgtexts:
+            # delimiter transport-padding CRLF
+            self.write(self._NL + '--' + boundary + self._NL)
+            # body-part
+            self._fp.write(body_part)
+        # close-delimiter transport-padding
+        self.write(self._NL + '--' + boundary + '--' + self._NL)
+        if msg.epilogue is not None:
+            if self._mangle_from_:
+                epilogue = fcre.sub('>From ', msg.epilogue)
+            else:
+                epilogue = msg.epilogue
+            self._write_lines(epilogue)
+
+    def _handle_multipart_signed(self, msg):
+        # The contents of signed parts has to stay unmodified in order to keep
+        # the signature intact per RFC1847 2.1, so we disable header wrapping.
+        # RDM: This isn't enough to completely preserve the part, but it helps.
+        p = self.policy
+        self.policy = p.clone(max_line_length=0)
+        try:
+            self._handle_multipart(msg)
+        finally:
+            self.policy = p
+
+    def _handle_message_delivery_status(self, msg):
+        # We can't just write the headers directly to self's file object
+        # because this will leave an extra newline between the last header
+        # block and the boundary.  Sigh.
+        blocks = []
+        for part in msg.get_payload():
+            s = self._new_buffer()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False, linesep=self._NL)
+            text = s.getvalue()
+            lines = text.split(self._encoded_NL)
+            # Strip off the unnecessary trailing empty line
+            if lines and lines[-1] == self._encoded_EMPTY:
+                blocks.append(self._encoded_NL.join(lines[:-1]))
+            else:
+                blocks.append(text)
+        # Now join all the blocks with an empty line.  This has the lovely
+        # effect of separating each block with an empty line, but not adding
+        # an extra one after the last one.
+        self._fp.write(self._encoded_NL.join(blocks))
+
+    def _handle_message(self, msg):
+        s = self._new_buffer()
+        g = self.clone(s)
+        # The payload of a message/rfc822 part should be a multipart sequence
+        # of length 1.  The zeroth element of the list should be the Message
+        # object for the subpart.  Extract that object, stringify it, and
+        # write it out.
+        # Except, it turns out, when it's a string instead, which happens when
+        # and only when HeaderParser is used on a message of mime type
+        # message/rfc822.  Such messages are generated by, for example,
+        # Groupwise when forwarding unadorned messages.  (Issue 7970.)  So
+        # in that case we just emit the string body.
+        payload = msg._payload
+        if isinstance(payload, list):
+            g.flatten(msg.get_payload(0), unixfrom=False, linesep=self._NL)
+            payload = s.getvalue()
+        else:
+            payload = self._encode(payload)
+        self._fp.write(payload)
+
+    # This used to be a module level function; we use a classmethod for this
+    # and _compile_re so we can continue to provide the module level function
+    # for backward compatibility by doing
+    #   _make_boundary = Generator._make_boundary
+    # at the end of the module.  It *is* internal, so we could drop that...
+    @classmethod
+    def _make_boundary(cls, text=None):
+        # Craft a random boundary.  If text is given, ensure that the chosen
+        # boundary doesn't appear in the text.
+        token = random.randrange(sys.maxsize)
+        boundary = ('=' * 15) + (_fmt % token) + '=='
+        if text is None:
+            return boundary
+        b = boundary
+        counter = 0
+        while True:
+            cre = cls._compile_re('^--' + re.escape(b) + '(--)?$', re.MULTILINE)
+            if not cre.search(text):
+                break
+            b = boundary + '.' + str(counter)
+            counter += 1
+        return b
+
+    @classmethod
+    def _compile_re(cls, s, flags):
+        return re.compile(s, flags)
+
+
+class BytesGenerator(Generator):
+    """Generates a bytes version of a Message object tree.
+
+    Functionally identical to the base Generator except that the output is
+    bytes and not string.  When surrogates were used in the input to encode
+    bytes, these are decoded back to bytes for output.  If the policy has
+    cte_type set to 7bit, then the message is transformed such that the
+    non-ASCII bytes are properly content transfer encoded, using the charset
+    unknown-8bit.
+
+    The outfp object must accept bytes in its write method.
+    """
+
+    def write(self, s):
+        self._fp.write(s.encode('ascii', 'surrogateescape'))
+
+    def _new_buffer(self):
+        return BytesIO()
+
+    def _encode(self, s):
+        return s.encode('ascii')
+
+    def _write_headers(self, msg):
+        # This is almost the same as the string version, except for handling
+        # strings with 8bit bytes.
+        for h, v in msg.raw_items():
+            self._fp.write(self.policy.fold_binary(h, v))
+        # A blank line always separates headers from body
+        self.write(self._NL)
+
+    def _handle_text(self, msg):
+        # If the string has surrogates the original source was bytes, so
+        # just write it back out.
+        if msg._payload is None:
+            return
+        if _has_surrogates(msg._payload) and not self.policy.cte_type=='7bit':
+            if self._mangle_from_:
+                msg._payload = fcre.sub(">From ", msg._payload)
+            self._write_lines(msg._payload)
+        else:
+            super(BytesGenerator,self)._handle_text(msg)
+
+    # Default body handler
+    _writeBody = _handle_text
+
+    @classmethod
+    def _compile_re(cls, s, flags):
+        return re.compile(s.encode('ascii'), flags)
+
+
+
+_FMT = '[Non-text (%(type)s) part of message omitted, filename %(filename)s]'
+
+class DecodedGenerator(Generator):
+    """Generates a text representation of a message.
+
+    Like the Generator base class, except that non-text parts are substituted
+    with a format string representing the part.
+    """
+    def __init__(self, outfp, mangle_from_=None, maxheaderlen=None, fmt=None, *,
+                 policy=None):
+        """Like Generator.__init__() except that an additional optional
+        argument is allowed.
+
+        Walks through all subparts of a message.  If the subpart is of main
+        type `text', then it prints the decoded payload of the subpart.
+
+        Otherwise, fmt is a format string that is used instead of the message
+        payload.  fmt is expanded with the following keywords (in
+        %(keyword)s format):
+
+        type       : Full MIME type of the non-text part
+        maintype   : Main MIME type of the non-text part
+        subtype    : Sub-MIME type of the non-text part
+        filename   : Filename of the non-text part
+        description: Description associated with the non-text part
+        encoding   : Content transfer encoding of the non-text part
+
+        The default value for fmt is None, meaning
+
+        [Non-text (%(type)s) part of message omitted, filename %(filename)s]
+        """
+        Generator.__init__(self, outfp, mangle_from_, maxheaderlen,
+                           policy=policy)
+        if fmt is None:
+            self._fmt = _FMT
+        else:
+            self._fmt = fmt
+
+    def _dispatch(self, msg):
+        for part in msg.walk():
+            maintype = part.get_content_maintype()
+            if maintype == 'text':
+                print(part.get_payload(decode=False), file=self)
+            elif maintype == 'multipart':
+                # Just skip this
+                pass
+            else:
+                print(self._fmt % {
+                    'type'       : part.get_content_type(),
+                    'maintype'   : part.get_content_maintype(),
+                    'subtype'    : part.get_content_subtype(),
+                    'filename'   : part.get_filename('[no filename]'),
+                    'description': part.get('Content-Description',
+                                            '[no description]'),
+                    'encoding'   : part.get('Content-Transfer-Encoding',
+                                            '[no encoding]'),
+                    }, file=self)
+
+
+
+# Helper used by Generator._make_boundary
+_width = len(repr(sys.maxsize-1))
+_fmt = '%%0%dd' % _width
+
+# Backward compatibility
+_make_boundary = Generator._make_boundary
diff --git a/modules/language/python/module/email/headerregistry.py b/modules/language/python/module/email/headerregistry.py
new file mode 100644
index 0000000..6b8615d
--- /dev/null
+++ b/modules/language/python/module/email/headerregistry.py
@@ -0,0 +1,592 @@
+module(email,headerregistry)
+"""Representing and manipulating email headers via custom objects.
+
+This module provides an implementation of the HeaderRegistry API.
+The implementation is designed to flexibly follow RFC5322 rules.
+
+Eventually HeaderRegistry will be a public API, but it isn't yet,
+and will probably change some before that happens.
+
+"""
+
+__all__=['HeaderRegistry']
+
+from types import MappingProxyType
+import email.utils as utils
+import email.errors as errors
+import email._header_value_parser as parser
+
+class Address:
+
+    def __init__(self, display_name='', username='', domain='', addr_spec=None):
+        """Create an object representing a full email address.
+
+        An address can have a 'display_name', a 'username', and a 'domain'.  In
+        addition to specifying the username and domain separately, they may be
+        specified together by using the addr_spec keyword *instead of* the
+        username and domain keywords.  If an addr_spec string is specified it
+        must be properly quoted according to RFC 5322 rules; an error will be
+        raised if it is not.
+
+        An Address object has display_name, username, domain, and addr_spec
+        attributes, all of which are read-only.  The addr_spec and the string
+        value of the object are both quoted according to RFC5322 rules, but
+        without any Content Transfer Encoding.
+
+        """
+        # This clause with its potential 'raise' may only happen when an
+        # application program creates an Address object using an addr_spec
+        # keyword.  The email library code itself must always supply username
+        # and domain.
+        if addr_spec is not None:
+            if username or domain:
+                raise TypeError("addrspec specified when username and/or "
+                                "domain also specified")
+            a_s, rest = parser.get_addr_spec(addr_spec)
+            if rest:
+                raise ValueError("Invalid addr_spec; only '{}' "
+                                 "could be parsed from '{}'".format(
+                                    a_s, addr_spec))
+            if a_s.all_defects:
+                raise a_s.all_defects[0]
+            username = a_s.local_part
+            domain = a_s.domain
+        self._display_name = display_name
+        self._username = username
+        self._domain = domain
+
+    @property
+    def display_name(self):
+        return self._display_name
+
+    @property
+    def username(self):
+        return self._username
+
+    @property
+    def domain(self):
+        return self._domain
+
+    @property
+    def addr_spec(self):
+        """The addr_spec (username@domain) portion of the address, quoted
+        according to RFC 5322 rules, but with no Content Transfer Encoding.
+        """
+        nameset = set(self.username)
+        if len(nameset) > len(nameset-parser.DOT_ATOM_ENDS):
+            lp = parser.quote_string(self.username)
+        else:
+            lp = self.username
+        if self.domain:
+            return lp + '@' + self.domain
+        if not lp:
+            return '<>'
+        return lp
+
+    def __repr__(self):
+        return "{}(display_name={!r}, username={!r}, domain={!r})".format(
+                        self.__class__.__name__,
+                        self.display_name, self.username, self.domain)
+
+    def __str__(self):
+        nameset = set(self.display_name)
+        if len(nameset) > len(nameset-parser.SPECIALS):
+            disp = parser.quote_string(self.display_name)
+        else:
+            disp = self.display_name
+        if disp:
+            addr_spec = '' if self.addr_spec=='<>' else self.addr_spec
+            return "{} <{}>".format(disp, addr_spec)
+        return self.addr_spec
+
+    def __eq__(self, other):
+        if type(other) != type(self):
+            return False
+        return (self.display_name == other.display_name and
+                self.username == other.username and
+                self.domain == other.domain)
+
+
+class Group:
+
+    def __init__(self, display_name=None, addresses=None):
+        """Create an object representing an address group.
+
+        An address group consists of a display_name followed by colon and a
+        list of addresses (see Address) terminated by a semi-colon.  The Group
+        is created by specifying a display_name and a possibly empty list of
+        Address objects.  A Group can also be used to represent a single
+        address that is not in a group, which is convenient when manipulating
+        lists that are a combination of Groups and individual Addresses.  In
+        this case the display_name should be set to None.  In particular, the
+        string representation of a Group whose display_name is None is the same
+        as the Address object, if there is one and only one Address object in
+        the addresses list.
+
+        """
+        self._display_name = display_name
+        self._addresses = tuple(addresses) if addresses else tuple()
+
+    @property
+    def display_name(self):
+        return self._display_name
+
+    @property
+    def addresses(self):
+        return self._addresses
+
+    def __repr__(self):
+        return "{}(display_name={!r}, addresses={!r}".format(
+                 self.__class__.__name__,
+                 self.display_name, self.addresses)
+
+    def __str__(self):
+        if self.display_name is None and len(self.addresses)==1:
+            return str(self.addresses[0])
+        disp = self.display_name
+        if disp is not None:
+            nameset = set(disp)
+            if len(nameset) > len(nameset-parser.SPECIALS):
+                disp = parser.quote_string(disp)
+        adrstr = ", ".join(str(x) for x in self.addresses)
+        adrstr = ' ' + adrstr if adrstr else adrstr
+        return "{}:{};".format(disp, adrstr)
+
+    def __eq__(self, other):
+        if type(other) != type(self):
+            return False
+        return (self.display_name == other.display_name and
+                self.addresses == other.addresses)
+
+
+# Header Classes #
+
+class BaseHeader(str):
+
+    """Base class for message headers.
+
+    Implements generic behavior and provides tools for subclasses.
+
+    A subclass must define a classmethod named 'parse' that takes an unfolded
+    value string and a dictionary as its arguments.  The dictionary will
+    contain one key, 'defects', initialized to an empty list.  After the call
+    the dictionary must contain two additional keys: parse_tree, set to the
+    parse tree obtained from parsing the header, and 'decoded', set to the
+    string value of the idealized representation of the data from the value.
+    (That is, encoded words are decoded, and values that have canonical
+    representations are so represented.)
+
+    The defects key is intended to collect parsing defects, which the message
+    parser will subsequently dispose of as appropriate.  The parser should not,
+    insofar as practical, raise any errors.  Defects should be added to the
+    list instead.  The standard header parsers register defects for RFC
+    compliance issues, for obsolete RFC syntax, and for unrecoverable parsing
+    errors.
+
+    The parse method may add additional keys to the dictionary.  In this case
+    the subclass must define an 'init' method, which will be passed the
+    dictionary as its keyword arguments.  The method should use (usually by
+    setting them as the value of similarly named attributes) and remove all the
+    extra keys added by its parse method, and then use super to call its parent
+    class with the remaining arguments and keywords.
+
+    The subclass should also make sure that a 'max_count' attribute is defined
+    that is either None or 1. XXX: need to better define this API.
+
+    """
+
+    def __new__(cls, name, value):
+        kwds = {'defects': []}
+        cls.parse(value, kwds)
+        if utils._has_surrogates(kwds['decoded']):
+            kwds['decoded'] = utils._sanitize(kwds['decoded'])
+        self = str.__new__(cls, kwds['decoded'])
+        del kwds['decoded']
+        self.init(name, **kwds)
+        return self
+
+    def init(self, name, *, parse_tree, defects):
+        self._name = name
+        self._parse_tree = parse_tree
+        self._defects = defects
+
+    @property
+    def name(self):
+        return self._name
+
+    @property
+    def defects(self):
+        return tuple(self._defects)
+
+    def __reduce__(self):
+        return (
+            _reconstruct_header,
+            (
+                self.__class__.__name__,
+                self.__class__.__bases__,
+                str(self),
+            ),
+            self.__dict__)
+
+    @classmethod
+    def _reconstruct(cls, value):
+        return str.__new__(cls, value)
+
+    def fold(self, *, policy):
+        """Fold header according to policy.
+
+        The parsed representation of the header is folded according to
+        RFC5322 rules, as modified by the policy.  If the parse tree
+        contains surrogateescaped bytes, the bytes are CTE encoded using
+        the charset 'unknown-8bit".
+
+        Any non-ASCII characters in the parse tree are CTE encoded using
+        charset utf-8. XXX: make this a policy setting.
+
+        The returned value is an ASCII-only string possibly containing linesep
+        characters, and ending with a linesep character.  The string includes
+        the header name and the ': ' separator.
+
+        """
+        # At some point we need to put fws here iif it was in the source.
+        header = parser.Header([
+            parser.HeaderLabel([
+                parser.ValueTerminal(self.name, 'header-name'),
+                parser.ValueTerminal(':', 'header-sep')]),
+            ])
+        if self._parse_tree:
+            header.append(
+                parser.CFWSList([parser.WhiteSpaceTerminal(' ', 'fws')]))
+        header.append(self._parse_tree)
+        return header.fold(policy=policy)
+
+
+def _reconstruct_header(cls_name, bases, value):
+    return type(cls_name, bases, {})._reconstruct(value)
+
+
+class UnstructuredHeader:
+
+    max_count = None
+    value_parser = staticmethod(parser.get_unstructured)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = cls.value_parser(value)
+        kwds['decoded'] = str(kwds['parse_tree'])
+
+
+class UniqueUnstructuredHeader(UnstructuredHeader):
+
+    max_count = 1
+
+
+class DateHeader:
+
+    """Header whose value consists of a single timestamp.
+
+    Provides an additional attribute, datetime, which is either an aware
+    datetime using a timezone, or a naive datetime if the timezone
+    in the input string is -0000.  Also accepts a datetime as input.
+    The 'value' attribute is the normalized form of the timestamp,
+    which means it is the output of format_datetime on the datetime.
+    """
+
+    max_count = None
+
+    # This is used only for folding, not for creating 'decoded'.
+    value_parser = staticmethod(parser.get_unstructured)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        if not value:
+            kwds['defects'].append(errors.HeaderMissingRequiredValue())
+            kwds['datetime'] = None
+            kwds['decoded'] = ''
+            kwds['parse_tree'] = parser.TokenList()
+            return
+        if isinstance(value, str):
+            value = utils.parsedate_to_datetime(value)
+        kwds['datetime'] = value
+        kwds['decoded'] = utils.format_datetime(kwds['datetime'])
+        kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
+
+    def init(self, *args, **kw):
+        self._datetime = kw.pop('datetime')
+        super().init(*args, **kw)
+
+    @property
+    def datetime(self):
+        return self._datetime
+
+
+class UniqueDateHeader(DateHeader):
+
+    max_count = 1
+
+
+class AddressHeader:
+
+    max_count = None
+
+    @staticmethod
+    def value_parser(value):
+        address_list, value = parser.get_address_list(value)
+        assert not value, 'this should not happen'
+        return address_list
+
+    @classmethod
+    def parse(cls, value, kwds):
+        if isinstance(value, str):
+            # We are translating here from the RFC language (address/mailbox)
+            # to our API language (group/address).
+            kwds['parse_tree'] = address_list = cls.value_parser(value)
+            groups = []
+            for addr in address_list.addresses:
+                groups.append(Group(addr.display_name,
+                                    [Address(mb.display_name or '',
+                                             mb.local_part or '',
+                                             mb.domain or '')
+                                     for mb in addr.all_mailboxes]))
+            defects = list(address_list.all_defects)
+        else:
+            # Assume it is Address/Group stuff
+            if not hasattr(value, '__iter__'):
+                value = [value]
+            groups = [Group(None, [item]) if not hasattr(item, 'addresses')
+                                          else item
+                                    for item in value]
+            defects = []
+        kwds['groups'] = groups
+        kwds['defects'] = defects
+        kwds['decoded'] = ', '.join([str(item) for item in groups])
+        if 'parse_tree' not in kwds:
+            kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
+
+    def init(self, *args, **kw):
+        self._groups = tuple(kw.pop('groups'))
+        self._addresses = None
+        super().init(*args, **kw)
+
+    @property
+    def groups(self):
+        return self._groups
+
+    @property
+    def addresses(self):
+        if self._addresses is None:
+            self._addresses = tuple([address for group in self._groups
+                                             for address in group.addresses])
+        return self._addresses
+
+
+class UniqueAddressHeader(AddressHeader):
+
+    max_count = 1
+
+
+class SingleAddressHeader(AddressHeader):
+
+    @property
+    def address(self):
+        if len(self.addresses)!=1:
+            raise ValueError(("value of single address header {} is not "
+                "a single address").format(self.name))
+        return self.addresses[0]
+
+
+class UniqueSingleAddressHeader(SingleAddressHeader):
+
+    max_count = 1
+
+
+class MIMEVersionHeader:
+
+    max_count = 1
+
+    value_parser = staticmethod(parser.parse_mime_version)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+        kwds['major'] = None if parse_tree.minor is None else parse_tree.major
+        kwds['minor'] = parse_tree.minor
+        if parse_tree.minor is not None:
+            kwds['version'] = '{}.{}'.format(kwds['major'], kwds['minor'])
+        else:
+            kwds['version'] = None
+
+    def init(self, *args, **kw):
+        self._version = kw.pop('version')
+        self._major = kw.pop('major')
+        self._minor = kw.pop('minor')
+        super().init(*args, **kw)
+
+    @property
+    def major(self):
+        return self._major
+
+    @property
+    def minor(self):
+        return self._minor
+
+    @property
+    def version(self):
+        return self._version
+
+
+class ParameterizedMIMEHeader:
+
+    # Mixin that handles the params dict.  Must be subclassed and
+    # a property value_parser for the specific header provided.
+
+    max_count = 1
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+        if parse_tree.params is None:
+            kwds['params'] = {}
+        else:
+            # The MIME RFCs specify that parameter ordering is arbitrary.
+            kwds['params'] = {utils._sanitize(name).lower():
+                                    utils._sanitize(value)
+                               for name, value in parse_tree.params}
+
+    def init(self, *args, **kw):
+        self._params = kw.pop('params')
+        super().init(*args, **kw)
+
+    @property
+    def params(self):
+        return MappingProxyType(self._params)
+
+
+class ContentTypeHeader(ParameterizedMIMEHeader):
+
+    value_parser = staticmethod(parser.parse_content_type_header)
+
+    def init(self, *args, **kw):
+        super().init(*args, **kw)
+        self._maintype = utils._sanitize(self._parse_tree.maintype)
+        self._subtype = utils._sanitize(self._parse_tree.subtype)
+
+    @property
+    def maintype(self):
+        return self._maintype
+
+    @property
+    def subtype(self):
+        return self._subtype
+
+    @property
+    def content_type(self):
+        return self.maintype + '/' + self.subtype
+
+
+class ContentDispositionHeader(ParameterizedMIMEHeader):
+
+    value_parser = staticmethod(parser.parse_content_disposition_header)
+
+    def init(self, *args, **kw):
+        super().init(*args, **kw)
+        cd = self._parse_tree.content_disposition
+        self._content_disposition = cd if cd is None else utils._sanitize(cd)
+
+    @property
+    def content_disposition(self):
+        return self._content_disposition
+
+
+class ContentTransferEncodingHeader:
+
+    max_count = 1
+
+    value_parser = staticmethod(parser.parse_content_transfer_encoding_header)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+
+    def init(self, *args, **kw):
+        super().init(*args, **kw)
+        self._cte = utils._sanitize(self._parse_tree.cte)
+
+    @property
+    def cte(self):
+        return self._cte
+
+
+# The header factory #
+
+_default_header_map = {
+    'subject':                      UniqueUnstructuredHeader,
+    'date':                         UniqueDateHeader,
+    'resent-date':                  DateHeader,
+    'orig-date':                    UniqueDateHeader,
+    'sender':                       UniqueSingleAddressHeader,
+    'resent-sender':                SingleAddressHeader,
+    'to':                           UniqueAddressHeader,
+    'resent-to':                    AddressHeader,
+    'cc':                           UniqueAddressHeader,
+    'resent-cc':                    AddressHeader,
+    'bcc':                          UniqueAddressHeader,
+    'resent-bcc':                   AddressHeader,
+    'from':                         UniqueAddressHeader,
+    'resent-from':                  AddressHeader,
+    'reply-to':                     UniqueAddressHeader,
+    'mime-version':                 MIMEVersionHeader,
+    'content-type':                 ContentTypeHeader,
+    'content-disposition':          ContentDispositionHeader,
+    'content-transfer-encoding':    ContentTransferEncodingHeader,
+    }
+
+class HeaderRegistry:
+
+    """A header_factory and header registry."""
+
+    def __init__(self, base_class=BaseHeader, default_class=UnstructuredHeader,
+                       use_default_map=True):
+        """Create a header_factory that works with the Policy API.
+
+        base_class is the class that will be the last class in the created
+        header class's __bases__ list.  default_class is the class that will be
+        used if "name" (see __call__) does not appear in the registry.
+        use_default_map controls whether or not the default mapping of names to
+        specialized classes is copied in to the registry when the factory is
+        created.  The default is True.
+
+        """
+        self.registry = {}
+        self.base_class = base_class
+        self.default_class = default_class
+        if use_default_map:
+            self.registry.update(_default_header_map)
+
+    def map_to_type(self, name, cls):
+        """Register cls as the specialized class for handling "name" headers.
+
+        """
+        self.registry[name.lower()] = cls
+
+    def __getitem__(self, name):
+        cls = self.registry.get(name.lower(), self.default_class)
+        return type('_'+cls.__name__, (cls, self.base_class), {})
+
+    def __call__(self, name, value):
+        """Create a header instance for header 'name' from 'value'.
+
+        Creates a header instance by creating a specialized class for parsing
+        and representing the specified header by combining the factory
+        base_class with a specialized class from the registry or the
+        default_class, and passing the name and value to the constructed
+        class's constructor.
+
+        """
+        return self[name](name, value)
diff --git a/modules/language/python/module/email/iterators.py b/modules/language/python/module/email/iterators.py
new file mode 100644
index 0000000..0773bdf
--- /dev/null
+++ b/modules/language/python/module/email/iterators.py
@@ -0,0 +1,72 @@
+module(email,iterators)
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Various types of useful iterators and generators."""
+
+__all__ = [
+    'body_line_iterator',
+    'typed_subpart_iterator',
+    'walk',
+    # Do not include _structure() since it's part of the debugging API.
+    ]
+
+import sys
+from io import StringIO
+
+
+
+# This function will become a method of the Message class
+def walk(self):
+    """Walk over the message tree, yielding each subpart.
+
+    The walk is performed in depth-first order.  This method is a
+    generator.
+    """
+    yield self
+    if self.is_multipart():
+        for subpart in self.get_payload():
+            yield from subpart.walk()
+
+
+
+# These two functions are imported into the Iterators.py interface module.
+def body_line_iterator(msg, decode=False):
+    """Iterate over the parts, returning string payloads line-by-line.
+
+    Optional decode (default False) is passed through to .get_payload().
+    """
+    for subpart in msg.walk():
+        payload = subpart.get_payload(decode=decode)
+        if isinstance(payload, str):
+            yield from StringIO(payload)
+
+
+def typed_subpart_iterator(msg, maintype='text', subtype=None):
+    """Iterate over the subparts with a given MIME type.
+
+    Use `maintype' as the main MIME type to match against; this defaults to
+    "text".  Optional `subtype' is the MIME subtype to match against; if
+    omitted, only the main type is matched.
+    """
+    for subpart in msg.walk():
+        if subpart.get_content_maintype() == maintype:
+            if subtype is None or subpart.get_content_subtype() == subtype:
+                yield subpart
+
+
+
+def _structure(msg, fp=None, level=0, include_default=False):
+    """A handy debugging aid"""
+    if fp is None:
+        fp = sys.stdout
+    tab = ' ' * (level * 4)
+    print(tab + msg.get_content_type(), end='', file=fp)
+    if include_default:
+        print(' [%s]' % msg.get_default_type(), file=fp)
+    else:
+        print(file=fp)
+    if msg.is_multipart():
+        for subpart in msg.get_payload():
+            _structure(subpart, fp, level+1, include_default)
diff --git a/modules/language/python/module/email/message.py b/modules/language/python/module/email/message.py
new file mode 100644
index 0000000..c73aa3c
--- /dev/null
+++ b/modules/language/python/module/email/message.py
@@ -0,0 +1,1164 @@
+module(email,message)
+# Copyright (C) 2001-2007 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Basic message object for the email package object model."""
+
+__all__ = ['Message', 'EmailMessage']
+
+import re
+import uu
+import quopri
+from io import BytesIO, StringIO
+
+# Intrapackage imports
+import email.utils as utils
+import email.errors as errors
+from email._policybase import Policy, compat32
+import email.charset as _charset
+from email._encoded_words import decode_b
+Charset = _charset.Charset
+
+SEMISPACE = '; '
+
+# Regular expression that matches `special' characters in parameters, the
+# existence of which force quoting of the parameter value.
+tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
+
+
+def _splitparam(param):
+    # Split header parameters.  BAW: this may be too simple.  It isn't
+    # strictly RFC 2045 (section 5.1) compliant, but it catches most headers
+    # found in the wild.  We may eventually need a full fledged parser.
+    # RDM: we might have a Header here; for now just stringify it.
+    a, sep, b = str(param).partition(';')
+    if not sep:
+        return a.strip(), None
+    return a.strip(), b.strip()
+
+def _formatparam(param, value=None, quote=True):
+    """Convenience function to format and return a key=value pair.
+
+    This will quote the value if needed or if quote is true.  If value is a
+    three tuple (charset, language, value), it will be encoded according
+    to RFC2231 rules.  If it contains non-ascii characters it will likewise
+    be encoded according to RFC2231 rules, using the utf-8 charset and
+    a null language.
+    """
+    if value is not None and len(value) > 0:
+        # A tuple is used for RFC 2231 encoded parameter values where items
+        # are (charset, language, value).  charset is a string, not a Charset
+        # instance.  RFC 2231 encoded values are never quoted, per RFC.
+        if isinstance(value, tuple):
+            # Encode as per RFC 2231
+            param += '*'
+            value = utils.encode_rfc2231(value[2], value[0], value[1])
+            return '%s=%s' % (param, value)
+        else:
+            try:
+                value.encode('ascii')
+            except UnicodeEncodeError:
+                param += '*'
+                value = utils.encode_rfc2231(value, 'utf-8', '')
+                return '%s=%s' % (param, value)
+        # BAW: Please check this.  I think that if quote is set it should
+        # force quoting even if not necessary.
+        if quote or tspecials.search(value):
+            return '%s="%s"' % (param, utils.quote(value))
+        else:
+            return '%s=%s' % (param, value)
+    else:
+        return param
+
+def _parseparam(s):
+    # RDM This might be a Header, so for now stringify it.
+    s = ';' + str(s)
+    plist = []
+    while s[:1] == ';':
+        s = s[1:]
+        end = s.find(';')
+        while end > 0 and (s.count('"', 0, end) - s.count('\\"', 0, end)) % 2:
+            end = s.find(';', end + 1)
+        if end < 0:
+            end = len(s)
+        f = s[:end]
+        if '=' in f:
+            i = f.index('=')
+            f = f[:i].strip().lower() + '=' + f[i+1:].strip()
+        plist.append(f.strip())
+        s = s[end:]
+    return plist
+
+
+def _unquotevalue(value):
+    # This is different than utils.collapse_rfc2231_value() because it doesn't
+    # try to convert the value to a unicode.  Message.get_param() and
+    # Message.get_params() are both currently defined to return the tuple in
+    # the face of RFC 2231 parameters.
+    if isinstance(value, tuple):
+        return value[0], value[1], utils.unquote(value[2])
+    else:
+        return utils.unquote(value)
+
+
+class Message:
+    """Basic message object.
+
+    A message object is defined as something that has a bunch of RFC 2822
+    headers and a payload.  It may optionally have an envelope header
+    (a.k.a. Unix-From or From_ header).  If the message is a container (i.e. a
+    multipart or a message/rfc822), then the payload is a list of Message
+    objects, otherwise it is a string.
+
+    Message objects implement part of the `mapping' interface, which assumes
+    there is exactly one occurrence of the header per message.  Some headers
+    do in fact appear multiple times (e.g. Received) and for those headers,
+    you must use the explicit API to set or get all the headers.  Not all of
+    the mapping methods are implemented.
+    """
+    def __init__(self, policy=compat32):
+        self.policy = policy
+        self._headers = []
+        self._unixfrom = None
+        self._payload = None
+        self._charset = None
+        # Defaults for multipart messages
+        self.preamble = self.epilogue = None
+        self.defects = []
+        # Default content type
+        self._default_type = 'text/plain'
+
+    def __str__(self):
+        """Return the entire formatted message as a string.
+        """
+        return self.as_string()
+
+    def as_string(self, unixfrom=False, maxheaderlen=0, policy=None):
+        """Return the entire formatted message as a string.
+
+        Optional 'unixfrom', when true, means include the Unix From_ envelope
+        header.  For backward compatibility reasons, if maxheaderlen is
+        not specified it defaults to 0, so you must override it explicitly
+        if you want a different maxheaderlen.  'policy' is passed to the
+        Generator instance used to serialize the mesasge; if it is not
+        specified the policy associated with the message instance is used.
+
+        If the message object contains binary data that is not encoded
+        according to RFC standards, the non-compliant data will be replaced by
+        unicode "unknown character" code points.
+        """
+        from email.generator import Generator
+        policy = self.policy if policy is None else policy
+        fp = StringIO()
+        g = Generator(fp,
+                      mangle_from_=False,
+                      maxheaderlen=maxheaderlen,
+                      policy=policy)
+        g.flatten(self, unixfrom=unixfrom)
+        return fp.getvalue()
+
+    def __bytes__(self):
+        """Return the entire formatted message as a bytes object.
+        """
+        return self.as_bytes()
+
+    def as_bytes(self, unixfrom=False, policy=None):
+        """Return the entire formatted message as a bytes object.
+
+        Optional 'unixfrom', when true, means include the Unix From_ envelope
+        header.  'policy' is passed to the BytesGenerator instance used to
+        serialize the message; if not specified the policy associated with
+        the message instance is used.
+        """
+        from email.generator import BytesGenerator
+        policy = self.policy if policy is None else policy
+        fp = BytesIO()
+        g = BytesGenerator(fp, mangle_from_=False, policy=policy)
+        g.flatten(self, unixfrom=unixfrom)
+        return fp.getvalue()
+
+    def is_multipart(self):
+        """Return True if the message consists of multiple parts."""
+        return isinstance(self._payload, list)
+
+    #
+    # Unix From_ line
+    #
+    def set_unixfrom(self, unixfrom):
+        self._unixfrom = unixfrom
+
+    def get_unixfrom(self):
+        return self._unixfrom
+
+    #
+    # Payload manipulation.
+    #
+    def attach(self, payload):
+        """Add the given payload to the current payload.
+
+        The current payload will always be a list of objects after this method
+        is called.  If you want to set the payload to a scalar object, use
+        set_payload() instead.
+        """
+        if self._payload is None:
+            self._payload = [payload]
+        else:
+            try:
+                self._payload.append(payload)
+            except AttributeError:
+                raise TypeError("Attach is not valid on a message with a"
+                                " non-multipart payload")
+
+    def get_payload(self, i=None, decode=False):
+        """Return a reference to the payload.
+
+        The payload will either be a list object or a string.  If you mutate
+        the list object, you modify the message's payload in place.  Optional
+        i returns that index into the payload.
+
+        Optional decode is a flag indicating whether the payload should be
+        decoded or not, according to the Content-Transfer-Encoding header
+        (default is False).
+
+        When True and the message is not a multipart, the payload will be
+        decoded if this header's value is `quoted-printable' or `base64'.  If
+        some other encoding is used, or the header is missing, or if the
+        payload has bogus data (i.e. bogus base64 or uuencoded data), the
+        payload is returned as-is.
+
+        If the message is a multipart and the decode flag is True, then None
+        is returned.
+        """
+        # Here is the logic table for this code, based on the email5.0.0 code:
+        #   i     decode  is_multipart  result
+        # ------  ------  ------------  ------------------------------
+        #  None   True    True          None
+        #   i     True    True          None
+        #  None   False   True          _payload (a list)
+        #   i     False   True          _payload element i (a Message)
+        #   i     False   False         error (not a list)
+        #   i     True    False         error (not a list)
+        #  None   False   False         _payload
+        #  None   True    False         _payload decoded (bytes)
+        # Note that Barry planned to factor out the 'decode' case, but that
+        # isn't so easy now that we handle the 8 bit data, which needs to be
+        # converted in both the decode and non-decode path.
+        if self.is_multipart():
+            if decode:
+                return None
+            if i is None:
+                return self._payload
+            else:
+                return self._payload[i]
+        # For backward compatibility, Use isinstance and this error message
+        # instead of the more logical is_multipart test.
+        if i is not None and not isinstance(self._payload, list):
+            raise TypeError('Expected list, got %s' % type(self._payload))
+        payload = self._payload
+        # cte might be a Header, so for now stringify it.
+        cte = str(self.get('content-transfer-encoding', '')).lower()
+        # payload may be bytes here.
+        if isinstance(payload, str):
+            if utils._has_surrogates(payload):
+                bpayload = payload.encode('ascii', 'surrogateescape')
+                if not decode:
+                    try:
+                        payload = bpayload.decode(self.get_param('charset', 'ascii'), 'replace')
+                    except LookupError:
+                        payload = bpayload.decode('ascii', 'replace')
+            elif decode:
+                try:
+                    bpayload = payload.encode('ascii')
+                except UnicodeError:
+                    # This won't happen for RFC compliant messages (messages
+                    # containing only ASCII code points in the unicode input).
+                    # If it does happen, turn the string into bytes in a way
+                    # guaranteed not to fail.
+                    bpayload = payload.encode('raw-unicode-escape')
+        if not decode:
+            return payload
+        if cte == 'quoted-printable':
+            return quopri.decodestring(bpayload)
+        elif cte == 'base64':
+            # XXX: this is a bit of a hack; decode_b should probably be factored
+            # out somewhere, but I haven't figured out where yet.
+            value, defects = decode_b(b''.join(bpayload.splitlines()))
+            for defect in defects:
+                self.policy.handle_defect(self, defect)
+            return value
+        elif cte in ('x-uuencode', 'uuencode', 'uue', 'x-uue'):
+            in_file = BytesIO(bpayload)
+            out_file = BytesIO()
+            try:
+                uu.decode(in_file, out_file, quiet=True)
+                return out_file.getvalue()
+            except uu.Error:
+                # Some decoding problem
+                return bpayload
+        if isinstance(payload, str):
+            return bpayload
+        return payload
+
+    def set_payload(self, payload, charset=None):
+        """Set the payload to the given value.
+
+        Optional charset sets the message's default character set.  See
+        set_charset() for details.
+        """
+        if hasattr(payload, 'encode'):
+            if charset is None:
+                self._payload = payload
+                return
+            if not isinstance(charset, Charset):
+                charset = Charset(charset)
+            payload = payload.encode(charset.output_charset)
+        if hasattr(payload, 'decode'):
+            self._payload = payload.decode('ascii', 'surrogateescape')
+        else:
+            self._payload = payload
+        if charset is not None:
+            self.set_charset(charset)
+
+    def set_charset(self, charset):
+        """Set the charset of the payload to a given character set.
+
+        charset can be a Charset instance, a string naming a character set, or
+        None.  If it is a string it will be converted to a Charset instance.
+        If charset is None, the charset parameter will be removed from the
+        Content-Type field.  Anything else will generate a TypeError.
+
+        The message will be assumed to be of type text/* encoded with
+        charset.input_charset.  It will be converted to charset.output_charset
+        and encoded properly, if needed, when generating the plain text
+        representation of the message.  MIME headers (MIME-Version,
+        Content-Type, Content-Transfer-Encoding) will be added as needed.
+        """
+        if charset is None:
+            self.del_param('charset')
+            self._charset = None
+            return
+        if not isinstance(charset, Charset):
+            charset = Charset(charset)
+        self._charset = charset
+        if 'MIME-Version' not in self:
+            self.add_header('MIME-Version', '1.0')
+        if 'Content-Type' not in self:
+            self.add_header('Content-Type', 'text/plain',
+                            charset=charset.get_output_charset())
+        else:
+            self.set_param('charset', charset.get_output_charset())
+        if charset != charset.get_output_charset():
+            self._payload = charset.body_encode(self._payload)
+        if 'Content-Transfer-Encoding' not in self:
+            cte = charset.get_body_encoding()
+            try:
+                cte(self)
+            except TypeError:
+                # This 'if' is for backward compatibility, it allows unicode
+                # through even though that won't work correctly if the
+                # message is serialized.
+                payload = self._payload
+                if payload:
+                    try:
+                        payload = payload.encode('ascii', 'surrogateescape')
+                    except UnicodeError:
+                        payload = payload.encode(charset.output_charset)
+                self._payload = charset.body_encode(payload)
+                self.add_header('Content-Transfer-Encoding', cte)
+
+    def get_charset(self):
+        """Return the Charset instance associated with the message's payload.
+        """
+        return self._charset
+
+    #
+    # MAPPING INTERFACE (partial)
+    #
+    def __len__(self):
+        """Return the total number of headers, including duplicates."""
+        return len(self._headers)
+
+    def __getitem__(self, name):
+        """Get a header value.
+
+        Return None if the header is missing instead of raising an exception.
+
+        Note that if the header appeared multiple times, exactly which
+        occurrence gets returned is undefined.  Use get_all() to get all
+        the values matching a header field name.
+        """
+        return self.get(name)
+
+    def __setitem__(self, name, val):
+        """Set the value of a header.
+
+        Note: this does not overwrite an existing header with the same field
+        name.  Use __delitem__() first to delete any existing headers.
+        """
+        max_count = self.policy.header_max_count(name)
+        if max_count:
+            lname = name.lower()
+            found = 0
+            for k, v in self._headers:
+                if k.lower() == lname:
+                    found += 1
+                    if found >= max_count:
+                        raise ValueError("There may be at most {} {} headers "
+                                         "in a message".format(max_count, name))
+        self._headers.append(self.policy.header_store_parse(name, val))
+
+    def __delitem__(self, name):
+        """Delete all occurrences of a header, if present.
+
+        Does not raise an exception if the header is missing.
+        """
+        name = name.lower()
+        newheaders = []
+        for k, v in self._headers:
+            if k.lower() != name:
+                newheaders.append((k, v))
+        self._headers = newheaders
+
+    def __contains__(self, name):
+        return name.lower() in [k.lower() for k, v in self._headers]
+
+    def __iter__(self):
+        for field, value in self._headers:
+            yield field
+
+    def keys(self):
+        """Return a list of all the message's header field names.
+
+        These will be sorted in the order they appeared in the original
+        message, or were added to the message, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [k for k, v in self._headers]
+
+    def values(self):
+        """Return a list of all the message's header values.
+
+        These will be sorted in the order they appeared in the original
+        message, or were added to the message, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [self.policy.header_fetch_parse(k, v)
+                for k, v in self._headers]
+
+    def items(self):
+        """Get all the message's header fields and values.
+
+        These will be sorted in the order they appeared in the original
+        message, or were added to the message, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [(k, self.policy.header_fetch_parse(k, v))
+                for k, v in self._headers]
+
+    def get(self, name, failobj=None):
+        """Get a header value.
+
+        Like __getitem__() but return failobj instead of None when the field
+        is missing.
+        """
+        name = name.lower()
+        for k, v in self._headers:
+            if k.lower() == name:
+                return self.policy.header_fetch_parse(k, v)
+        return failobj
+
+    #
+    # "Internal" methods (public API, but only intended for use by a parser
+    # or generator, not normal application code.
+    #
+
+    def set_raw(self, name, value):
+        """Store name and value in the model without modification.
+
+        This is an "internal" API, intended only for use by a parser.
+        """
+        self._headers.append((name, value))
+
+    def raw_items(self):
+        """Return the (name, value) header pairs without modification.
+
+        This is an "internal" API, intended only for use by a generator.
+        """
+        return iter(self._headers.copy())
+
+    #
+    # Additional useful stuff
+    #
+
+    def get_all(self, name, failobj=None):
+        """Return a list of all the values for the named field.
+
+        These will be sorted in the order they appeared in the original
+        message, and may contain duplicates.  Any fields deleted and
+        re-inserted are always appended to the header list.
+
+        If no such fields exist, failobj is returned (defaults to None).
+        """
+        values = []
+        name = name.lower()
+        for k, v in self._headers:
+            if k.lower() == name:
+                values.append(self.policy.header_fetch_parse(k, v))
+        if not values:
+            return failobj
+        return values
+
+    def add_header(self, _name, _value, **_params):
+        """Extended header setting.
+
+        name is the header field to add.  keyword arguments can be used to set
+        additional parameters for the header field, with underscores converted
+        to dashes.  Normally the parameter will be added as key="value" unless
+        value is None, in which case only the key will be added.  If a
+        parameter value contains non-ASCII characters it can be specified as a
+        three-tuple of (charset, language, value), in which case it will be
+        encoded according to RFC2231 rules.  Otherwise it will be encoded using
+        the utf-8 charset and a language of ''.
+
+        Examples:
+
+        msg.add_header('content-disposition', 'attachment', filename='bud.gif')
+        msg.add_header('content-disposition', 'attachment',
+                       filename=('utf-8', '', Fußballer.ppt'))
+        msg.add_header('content-disposition', 'attachment',
+                       filename='Fußballer.ppt'))
+        """
+        parts = []
+        for k, v in _params.items():
+            if v is None:
+                parts.append(k.replace('_', '-'))
+            else:
+                parts.append(_formatparam(k.replace('_', '-'), v))
+        if _value is not None:
+            parts.insert(0, _value)
+        self[_name] = SEMISPACE.join(parts)
+
+    def replace_header(self, _name, _value):
+        """Replace a header.
+
+        Replace the first matching header found in the message, retaining
+        header order and case.  If no matching header was found, a KeyError is
+        raised.
+        """
+        _name = _name.lower()
+        for i, (k, v) in zip(range(len(self._headers)), self._headers):
+            if k.lower() == _name:
+                self._headers[i] = self.policy.header_store_parse(k, _value)
+                break
+        else:
+            raise KeyError(_name)
+
+    #
+    # Use these three methods instead of the three above.
+    #
+
+    def get_content_type(self):
+        """Return the message's content type.
+
+        The returned string is coerced to lower case of the form
+        `maintype/subtype'.  If there was no Content-Type header in the
+        message, the default type as given by get_default_type() will be
+        returned.  Since according to RFC 2045, messages always have a default
+        type this will always return a value.
+
+        RFC 2045 defines a message's default type to be text/plain unless it
+        appears inside a multipart/digest container, in which case it would be
+        message/rfc822.
+        """
+        missing = object()
+        value = self.get('content-type', missing)
+        if value is missing:
+            # This should have no parameters
+            return self.get_default_type()
+        ctype = _splitparam(value)[0].lower()
+        # RFC 2045, section 5.2 says if its invalid, use text/plain
+        if ctype.count('/') != 1:
+            return 'text/plain'
+        return ctype
+
+    def get_content_maintype(self):
+        """Return the message's main content type.
+
+        This is the `maintype' part of the string returned by
+        get_content_type().
+        """
+        ctype = self.get_content_type()
+        return ctype.split('/')[0]
+
+    def get_content_subtype(self):
+        """Returns the message's sub-content type.
+
+        This is the `subtype' part of the string returned by
+        get_content_type().
+        """
+        ctype = self.get_content_type()
+        return ctype.split('/')[1]
+
+    def get_default_type(self):
+        """Return the `default' content type.
+
+        Most messages have a default content type of text/plain, except for
+        messages that are subparts of multipart/digest containers.  Such
+        subparts have a default content type of message/rfc822.
+        """
+        return self._default_type
+
+    def set_default_type(self, ctype):
+        """Set the `default' content type.
+
+        ctype should be either "text/plain" or "message/rfc822", although this
+        is not enforced.  The default content type is not stored in the
+        Content-Type header.
+        """
+        self._default_type = ctype
+
+    def _get_params_preserve(self, failobj, header):
+        # Like get_params() but preserves the quoting of values.  BAW:
+        # should this be part of the public interface?
+        missing = object()
+        value = self.get(header, missing)
+        if value is missing:
+            return failobj
+        params = []
+        for p in _parseparam(value):
+            try:
+                name, val = p.split('=', 1)
+                name = name.strip()
+                val = val.strip()
+            except ValueError:
+                # Must have been a bare attribute
+                name = p.strip()
+                val = ''
+            params.append((name, val))
+        params = utils.decode_params(params)
+        return params
+
+    def get_params(self, failobj=None, header='content-type', unquote=True):
+        """Return the message's Content-Type parameters, as a list.
+
+        The elements of the returned list are 2-tuples of key/value pairs, as
+        split on the `=' sign.  The left hand side of the `=' is the key,
+        while the right hand side is the value.  If there is no `=' sign in
+        the parameter the value is the empty string.  The value is as
+        described in the get_param() method.
+
+        Optional failobj is the object to return if there is no Content-Type
+        header.  Optional header is the header to search instead of
+        Content-Type.  If unquote is True, the value is unquoted.
+        """
+        missing = object()
+        params = self._get_params_preserve(missing, header)
+        if params is missing:
+            return failobj
+        if unquote:
+            return [(k, _unquotevalue(v)) for k, v in params]
+        else:
+            return params
+
+    def get_param(self, param, failobj=None, header='content-type',
+                  unquote=True):
+        """Return the parameter value if found in the Content-Type header.
+
+        Optional failobj is the object to return if there is no Content-Type
+        header, or the Content-Type header has no such parameter.  Optional
+        header is the header to search instead of Content-Type.
+
+        Parameter keys are always compared case insensitively.  The return
+        value can either be a string, or a 3-tuple if the parameter was RFC
+        2231 encoded.  When it's a 3-tuple, the elements of the value are of
+        the form (CHARSET, LANGUAGE, VALUE).  Note that both CHARSET and
+        LANGUAGE can be None, in which case you should consider VALUE to be
+        encoded in the us-ascii charset.  You can usually ignore LANGUAGE.
+        The parameter value (either the returned string, or the VALUE item in
+        the 3-tuple) is always unquoted, unless unquote is set to False.
+
+        If your application doesn't care whether the parameter was RFC 2231
+        encoded, it can turn the return value into a string as follows:
+
+            rawparam = msg.get_param('foo')
+            param = email.utils.collapse_rfc2231_value(rawparam)
+
+        """
+        if header not in self:
+            return failobj
+        for k, v in self._get_params_preserve(failobj, header):
+            if k.lower() == param.lower():
+                if unquote:
+                    return _unquotevalue(v)
+                else:
+                    return v
+        return failobj
+
+    def set_param(self, param, value, header='Content-Type', requote=True,
+                  charset=None, language='', replace=False):
+        """Set a parameter in the Content-Type header.
+
+        If the parameter already exists in the header, its value will be
+        replaced with the new value.
+
+        If header is Content-Type and has not yet been defined for this
+        message, it will be set to "text/plain" and the new parameter and
+        value will be appended as per RFC 2045.
+
+        An alternate header can be specified in the header argument, and all
+        parameters will be quoted as necessary unless requote is False.
+
+        If charset is specified, the parameter will be encoded according to RFC
+        2231.  Optional language specifies the RFC 2231 language, defaulting
+        to the empty string.  Both charset and language should be strings.
+        """
+        if not isinstance(value, tuple) and charset:
+            value = (charset, language, value)
+
+        if header not in self and header.lower() == 'content-type':
+            ctype = 'text/plain'
+        else:
+            ctype = self.get(header)
+        if not self.get_param(param, header=header):
+            if not ctype:
+                ctype = _formatparam(param, value, requote)
+            else:
+                ctype = SEMISPACE.join(
+                    [ctype, _formatparam(param, value, requote)])
+        else:
+            ctype = ''
+            for old_param, old_value in self.get_params(header=header,
+                                                        unquote=requote):
+                append_param = ''
+                if old_param.lower() == param.lower():
+                    append_param = _formatparam(param, value, requote)
+                else:
+                    append_param = _formatparam(old_param, old_value, requote)
+                if not ctype:
+                    ctype = append_param
+                else:
+                    ctype = SEMISPACE.join([ctype, append_param])
+        if ctype != self.get(header):
+            if replace:
+                self.replace_header(header, ctype)
+            else:
+                del self[header]
+                self[header] = ctype
+
+    def del_param(self, param, header='content-type', requote=True):
+        """Remove the given parameter completely from the Content-Type header.
+
+        The header will be re-written in place without the parameter or its
+        value. All values will be quoted as necessary unless requote is
+        False.  Optional header specifies an alternative to the Content-Type
+        header.
+        """
+        if header not in self:
+            return
+        new_ctype = ''
+        for p, v in self.get_params(header=header, unquote=requote):
+            if p.lower() != param.lower():
+                if not new_ctype:
+                    new_ctype = _formatparam(p, v, requote)
+                else:
+                    new_ctype = SEMISPACE.join([new_ctype,
+                                                _formatparam(p, v, requote)])
+        if new_ctype != self.get(header):
+            del self[header]
+            self[header] = new_ctype
+
+    def set_type(self, type, header='Content-Type', requote=True):
+        """Set the main type and subtype for the Content-Type header.
+
+        type must be a string in the form "maintype/subtype", otherwise a
+        ValueError is raised.
+
+        This method replaces the Content-Type header, keeping all the
+        parameters in place.  If requote is False, this leaves the existing
+        header's quoting as is.  Otherwise, the parameters will be quoted (the
+        default).
+
+        An alternative header can be specified in the header argument.  When
+        the Content-Type header is set, we'll always also add a MIME-Version
+        header.
+        """
+        # BAW: should we be strict?
+        if not type.count('/') == 1:
+            raise ValueError
+        # Set the Content-Type, you get a MIME-Version
+        if header.lower() == 'content-type':
+            del self['mime-version']
+            self['MIME-Version'] = '1.0'
+        if header not in self:
+            self[header] = type
+            return
+        params = self.get_params(header=header, unquote=requote)
+        del self[header]
+        self[header] = type
+        # Skip the first param; it's the old type.
+        for p, v in params[1:]:
+            self.set_param(p, v, header, requote)
+
+    def get_filename(self, failobj=None):
+        """Return the filename associated with the payload if present.
+
+        The filename is extracted from the Content-Disposition header's
+        `filename' parameter, and it is unquoted.  If that header is missing
+        the `filename' parameter, this method falls back to looking for the
+        `name' parameter.
+        """
+        missing = object()
+        filename = self.get_param('filename', missing, 'content-disposition')
+        if filename is missing:
+            filename = self.get_param('name', missing, 'content-type')
+        if filename is missing:
+            return failobj
+        return utils.collapse_rfc2231_value(filename).strip()
+
+    def get_boundary(self, failobj=None):
+        """Return the boundary associated with the payload if present.
+
+        The boundary is extracted from the Content-Type header's `boundary'
+        parameter, and it is unquoted.
+        """
+        missing = object()
+        boundary = self.get_param('boundary', missing)
+        if boundary is missing:
+            return failobj
+        # RFC 2046 says that boundaries may begin but not end in w/s
+        return utils.collapse_rfc2231_value(boundary).rstrip()
+
+    def set_boundary(self, boundary):
+        """Set the boundary parameter in Content-Type to 'boundary'.
+
+        This is subtly different than deleting the Content-Type header and
+        adding a new one with a new boundary parameter via add_header().  The
+        main difference is that using the set_boundary() method preserves the
+        order of the Content-Type header in the original message.
+
+        HeaderParseError is raised if the message has no Content-Type header.
+        """
+        missing = object()
+        params = self._get_params_preserve(missing, 'content-type')
+        if params is missing:
+            # There was no Content-Type header, and we don't know what type
+            # to set it to, so raise an exception.
+            raise errors.HeaderParseError('No Content-Type header found')
+        newparams = []
+        foundp = False
+        for pk, pv in params:
+            if pk.lower() == 'boundary':
+                newparams.append(('boundary', '"%s"' % boundary))
+                foundp = True
+            else:
+                newparams.append((pk, pv))
+        if not foundp:
+            # The original Content-Type header had no boundary attribute.
+            # Tack one on the end.  BAW: should we raise an exception
+            # instead???
+            newparams.append(('boundary', '"%s"' % boundary))
+        # Replace the existing Content-Type header with the new value
+        newheaders = []
+        for h, v in self._headers:
+            if h.lower() == 'content-type':
+                parts = []
+                for k, v in newparams:
+                    if v == '':
+                        parts.append(k)
+                    else:
+                        parts.append('%s=%s' % (k, v))
+                val = SEMISPACE.join(parts)
+                newheaders.append(self.policy.header_store_parse(h, val))
+
+            else:
+                newheaders.append((h, v))
+        self._headers = newheaders
+
+    def get_content_charset(self, failobj=None):
+        """Return the charset parameter of the Content-Type header.
+
+        The returned string is always coerced to lower case.  If there is no
+        Content-Type header, or if that header has no charset parameter,
+        failobj is returned.
+        """
+        missing = object()
+        charset = self.get_param('charset', missing)
+        if charset is missing:
+            return failobj
+        if isinstance(charset, tuple):
+            # RFC 2231 encoded, so decode it, and it better end up as ascii.
+            pcharset = charset[0] or 'us-ascii'
+            try:
+                # LookupError will be raised if the charset isn't known to
+                # Python.  UnicodeError will be raised if the encoded text
+                # contains a character not in the charset.
+                as_bytes = charset[2].encode('raw-unicode-escape')
+                charset = str(as_bytes, pcharset)
+            except (LookupError, UnicodeError):
+                charset = charset[2]
+        # charset characters must be in us-ascii range
+        try:
+            charset.encode('us-ascii')
+        except UnicodeError:
+            return failobj
+        # RFC 2046, $4.1.2 says charsets are not case sensitive
+        return charset.lower()
+
+    def get_charsets(self, failobj=None):
+        """Return a list containing the charset(s) used in this message.
+
+        The returned list of items describes the Content-Type headers'
+        charset parameter for this message and all the subparts in its
+        payload.
+
+        Each item will either be a string (the value of the charset parameter
+        in the Content-Type header of that part) or the value of the
+        'failobj' parameter (defaults to None), if the part does not have a
+        main MIME type of "text", or the charset is not defined.
+
+        The list will contain one string for each part of the message, plus
+        one for the container message (i.e. self), so that a non-multipart
+        message will still return a list of length 1.
+        """
+        return [part.get_content_charset(failobj) for part in self.walk()]
+
+    def get_content_disposition(self):
+        """Return the message's content-disposition if it exists, or None.
+
+        The return values can be either 'inline', 'attachment' or None
+        according to the rfc2183.
+        """
+        value = self.get('content-disposition')
+        if value is None:
+            return None
+        c_d = _splitparam(value)[0].lower()
+        return c_d
+
+    # I.e. def walk(self): ...
+    from email.iterators import walk
+
+
+class MIMEPart(Message):
+
+    def __init__(self, policy=None):
+        if policy is None:
+            from email.policy import default
+            policy = default
+        Message.__init__(self, policy)
+
+
+    def as_string(self, unixfrom=False, maxheaderlen=None, policy=None):
+        """Return the entire formatted message as a string.
+
+        Optional 'unixfrom', when true, means include the Unix From_ envelope
+        header.  maxheaderlen is retained for backward compatibility with the
+        base Message class, but defaults to None, meaning that the policy value
+        for max_line_length controls the header maximum length.  'policy' is
+        passed to the Generator instance used to serialize the mesasge; if it
+        is not specified the policy associated with the message instance is
+        used.
+        """
+        policy = self.policy if policy is None else policy
+        if maxheaderlen is None:
+            maxheaderlen = policy.max_line_length
+        return super().as_string(maxheaderlen=maxheaderlen, policy=policy)
+
+    def __str__(self):
+        return self.as_string(policy=self.policy.clone(utf8=True))
+
+    def is_attachment(self):
+        c_d = self.get('content-disposition')
+        return False if c_d is None else c_d.content_disposition == 'attachment'
+
+    def _find_body(self, part, preferencelist):
+        if part.is_attachment():
+            return
+        maintype, subtype = part.get_content_type().split('/')
+        if maintype == 'text':
+            if subtype in preferencelist:
+                yield (preferencelist.index(subtype), part)
+            return
+        if maintype != 'multipart':
+            return
+        if subtype != 'related':
+            for subpart in part.iter_parts():
+                yield from self._find_body(subpart, preferencelist)
+            return
+        if 'related' in preferencelist:
+            yield (preferencelist.index('related'), part)
+        candidate = None
+        start = part.get_param('start')
+        if start:
+            for subpart in part.iter_parts():
+                if subpart['content-id'] == start:
+                    candidate = subpart
+                    break
+        if candidate is None:
+            subparts = part.get_payload()
+            candidate = subparts[0] if subparts else None
+        if candidate is not None:
+            yield from self._find_body(candidate, preferencelist)
+
+    def get_body(self, preferencelist=('related', 'html', 'plain')):
+        """Return best candidate mime part for display as 'body' of message.
+
+        Do a depth first search, starting with self, looking for the first part
+        matching each of the items in preferencelist, and return the part
+        corresponding to the first item that has a match, or None if no items
+        have a match.  If 'related' is not included in preferencelist, consider
+        the root part of any multipart/related encountered as a candidate
+        match.  Ignore parts with 'Content-Disposition: attachment'.
+        """
+        best_prio = len(preferencelist)
+        body = None
+        for prio, part in self._find_body(self, preferencelist):
+            if prio < best_prio:
+                best_prio = prio
+                body = part
+                if prio == 0:
+                    break
+        return body
+
+    _body_types = {('text', 'plain'),
+                   ('text', 'html'),
+                   ('multipart', 'related'),
+                   ('multipart', 'alternative')}
+    def iter_attachments(self):
+        """Return an iterator over the non-main parts of a multipart.
+
+        Skip the first of each occurrence of text/plain, text/html,
+        multipart/related, or multipart/alternative in the multipart (unless
+        they have a 'Content-Disposition: attachment' header) and include all
+        remaining subparts in the returned iterator.  When applied to a
+        multipart/related, return all parts except the root part.  Return an
+        empty iterator when applied to a multipart/alternative or a
+        non-multipart.
+        """
+        maintype, subtype = self.get_content_type().split('/')
+        if maintype != 'multipart' or subtype == 'alternative':
+            return
+        parts = self.get_payload().copy()
+        if maintype == 'multipart' and subtype == 'related':
+            # For related, we treat everything but the root as an attachment.
+            # The root may be indicated by 'start'; if there's no start or we
+            # can't find the named start, treat the first subpart as the root.
+            start = self.get_param('start')
+            if start:
+                found = False
+                attachments = []
+                for part in parts:
+                    if part.get('content-id') == start:
+                        found = True
+                    else:
+                        attachments.append(part)
+                if found:
+                    yield from attachments
+                    return
+            parts.pop(0)
+            yield from parts
+            return
+        # Otherwise we more or less invert the remaining logic in get_body.
+        # This only really works in edge cases (ex: non-text related or
+        # alternatives) if the sending agent sets content-disposition.
+        seen = []   # Only skip the first example of each candidate type.
+        for part in parts:
+            maintype, subtype = part.get_content_type().split('/')
+            if ((maintype, subtype) in self._body_types and
+                    not part.is_attachment() and subtype not in seen):
+                seen.append(subtype)
+                continue
+            yield part
+
+    def iter_parts(self):
+        """Return an iterator over all immediate subparts of a multipart.
+
+        Return an empty iterator for a non-multipart.
+        """
+        if self.get_content_maintype() == 'multipart':
+            yield from self.get_payload()
+
+    def get_content(self, *args, content_manager=None, **kw):
+        if content_manager is None:
+            content_manager = self.policy.content_manager
+        return content_manager.get_content(self, *args, **kw)
+
+    def set_content(self, *args, content_manager=None, **kw):
+        if content_manager is None:
+            content_manager = self.policy.content_manager
+        content_manager.set_content(self, *args, **kw)
+
+    def _make_multipart(self, subtype, disallowed_subtypes, boundary):
+        if self.get_content_maintype() == 'multipart':
+            existing_subtype = self.get_content_subtype()
+            disallowed_subtypes = disallowed_subtypes + (subtype,)
+            if existing_subtype in disallowed_subtypes:
+                raise ValueError("Cannot convert {} to {}".format(
+                    existing_subtype, subtype))
+        keep_headers = []
+        part_headers = []
+        for name, value in self._headers:
+            if name.lower().startswith('content-'):
+                part_headers.append((name, value))
+            else:
+                keep_headers.append((name, value))
+        if part_headers:
+            # There is existing content, move it to the first subpart.
+            part = type(self)(policy=self.policy)
+            part._headers = part_headers
+            part._payload = self._payload
+            self._payload = [part]
+        else:
+            self._payload = []
+        self._headers = keep_headers
+        self['Content-Type'] = 'multipart/' + subtype
+        if boundary is not None:
+            self.set_param('boundary', boundary)
+
+    def make_related(self, boundary=None):
+        self._make_multipart('related', ('alternative', 'mixed'), boundary)
+
+    def make_alternative(self, boundary=None):
+        self._make_multipart('alternative', ('mixed',), boundary)
+
+    def make_mixed(self, boundary=None):
+        self._make_multipart('mixed', (), boundary)
+
+    def _add_multipart(self, _subtype, *args, _disp=None, **kw):
+        if (self.get_content_maintype() != 'multipart' or
+                self.get_content_subtype() != _subtype):
+            getattr(self, 'make_' + _subtype)()
+        part = type(self)(policy=self.policy)
+        part.set_content(*args, **kw)
+        if _disp and 'content-disposition' not in part:
+            part['Content-Disposition'] = _disp
+        self.attach(part)
+
+    def add_related(self, *args, **kw):
+        self._add_multipart('related', *args, _disp='inline', **kw)
+
+    def add_alternative(self, *args, **kw):
+        self._add_multipart('alternative', *args, **kw)
+
+    def add_attachment(self, *args, **kw):
+        self._add_multipart('mixed', *args, _disp='attachment', **kw)
+
+    def clear(self):
+        self._headers = []
+        self._payload = None
+
+    def clear_content(self):
+        self._headers = [(n, v) for n, v in self._headers
+                         if not n.lower().startswith('content-')]
+        self._payload = None
+
+
+class EmailMessage(MIMEPart):
+
+    def set_content(self, *args, **kw):
+        super().set_content(*args, **kw)
+        if 'MIME-Version' not in self:
+            self['MIME-Version'] = '1.0'
diff --git a/modules/language/python/module/email/parser.py b/modules/language/python/module/email/parser.py
index 5ec164e..962f9dc 100644
--- a/modules/language/python/module/email/parser.py
+++ b/modules/language/python/module/email/parser.py
@@ -9,7 +9,6 @@ __all__ = ['Parser', 'HeaderParser', 'BytesParser', 'BytesHeaderParser',
            'FeedParser', 'BytesFeedParser']
 
 from io import StringIO, TextIOWrapper
-
 from email.feedparser import FeedParser, BytesFeedParser
 from email._policybase import compat32
 
diff --git a/modules/language/python/module/email/policy.py b/modules/language/python/module/email/policy.py
new file mode 100644
index 0000000..3f8551c
--- /dev/null
+++ b/modules/language/python/module/email/policy.py
@@ -0,0 +1,231 @@
+module(email,policy)
+"""This will be the home for the policy that hooks in the new
+code that adds all the email6 features.
+"""
+
+import re
+from email._policybase import Policy, Compat32, compat32, _extend_docstrings
+from email.utils import _has_surrogates
+from email.headerregistry import HeaderRegistry as HeaderRegistry
+from email.contentmanager import raw_data_manager
+from email.message import EmailMessage
+
+__all__ = [
+    'Compat32',
+    'compat32',
+    'Policy',
+    'EmailPolicy',
+    'default',
+    'strict',
+    'SMTP',
+    'HTTP',
+    ]
+
+linesep_splitter = re.compile(r'\n|\r')
+
+@_extend_docstrings
+class EmailPolicy(Policy):
+
+    """+
+    PROVISIONAL
+
+    The API extensions enabled by this policy are currently provisional.
+    Refer to the documentation for details.
+
+    This policy adds new header parsing and folding algorithms.  Instead of
+    simple strings, headers are custom objects with custom attributes
+    depending on the type of the field.  The folding algorithm fully
+    implements RFCs 2047 and 5322.
+
+    In addition to the settable attributes listed above that apply to
+    all Policies, this policy adds the following additional attributes:
+
+    utf8                -- if False (the default) message headers will be
+                           serialized as ASCII, using encoded words to encode
+                           any non-ASCII characters in the source strings.  If
+                           True, the message headers will be serialized using
+                           utf8 and will not contain encoded words (see RFC
+                           6532 for more on this serialization format).
+
+    refold_source       -- if the value for a header in the Message object
+                           came from the parsing of some source, this attribute
+                           indicates whether or not a generator should refold
+                           that value when transforming the message back into
+                           stream form.  The possible values are:
+
+                           none  -- all source values use original folding
+                           long  -- source values that have any line that is
+                                    longer than max_line_length will be
+                                    refolded
+                           all  -- all values are refolded.
+
+                           The default is 'long'.
+
+    header_factory      -- a callable that takes two arguments, 'name' and
+                           'value', where 'name' is a header field name and
+                           'value' is an unfolded header field value, and
+                           returns a string-like object that represents that
+                           header.  A default header_factory is provided that
+                           understands some of the RFC5322 header field types.
+                           (Currently address fields and date fields have
+                           special treatment, while all other fields are
+                           treated as unstructured.  This list will be
+                           completed before the extension is marked stable.)
+
+    content_manager     -- an object with at least two methods: get_content
+                           and set_content.  When the get_content or
+                           set_content method of a Message object is called,
+                           it calls the corresponding method of this object,
+                           passing it the message object as its first argument,
+                           and any arguments or keywords that were passed to
+                           it as additional arguments.  The default
+                           content_manager is
+                           :data:`~email.contentmanager.raw_data_manager`.
+
+    """
+
+    message_factory = EmailMessage
+    utf8 = False
+    refold_source = 'long'
+    header_factory = HeaderRegistry()
+    content_manager = raw_data_manager
+
+    def __init__(self, **kw):
+        # Ensure that each new instance gets a unique header factory
+        # (as opposed to clones, which share the factory).
+
+        if 'header_factory' not in kw:
+            object.__setattr__(self, 'header_factory', HeaderRegistry())
+
+        super().__init__(**kw)
+
+
+    def header_max_count(self, name):
+        """+
+        The implementation for this class returns the max_count attribute from
+        the specialized header class that would be used to construct a header
+        of type 'name'.
+        """
+        return self.header_factory[name].max_count
+
+    # The logic of the next three methods is chosen such that it is possible to
+    # switch a Message object between a Compat32 policy and a policy derived
+    # from this class and have the results stay consistent.  This allows a
+    # Message object constructed with this policy to be passed to a library
+    # that only handles Compat32 objects, or to receive such an object and
+    # convert it to use the newer style by just changing its policy.  It is
+    # also chosen because it postpones the relatively expensive full rfc5322
+    # parse until as late as possible when parsing from source, since in many
+    # applications only a few headers will actually be inspected.
+
+    def header_source_parse(self, sourcelines):
+        """+
+        The name is parsed as everything up to the ':' and returned unmodified.
+        The value is determined by stripping leading whitespace off the
+        remainder of the first line, joining all subsequent lines together, and
+        stripping any trailing carriage return or linefeed characters.  (This
+        is the same as Compat32).
+
+        """
+        name, value = sourcelines[0].split(':', 1)
+        value = value.lstrip(' \t') + ''.join(sourcelines[1:])
+        return (name, value.rstrip('\r\n'))
+
+    def header_store_parse(self, name, value):
+        """+
+        The name is returned unchanged.  If the input value has a 'name'
+        attribute and it matches the name ignoring case, the value is returned
+        unchanged.  Otherwise the name and value are passed to header_factory
+        method, and the resulting custom header object is returned as the
+        value.  In this case a ValueError is raised if the input value contains
+        CR or LF characters.
+
+        """
+        if hasattr(value, 'name') and value.name.lower() == name.lower():
+            return (name, value)
+        if isinstance(value, str) and len(value.splitlines())>1:
+            # XXX this error message isn't quite right when we use splitlines
+            # (see issue 22233), but I'm not sure what should happen here.
+            raise ValueError("Header values may not contain linefeed "
+                             "or carriage return characters")
+        return (name, self.header_factory(name, value))
+
+    def header_fetch_parse(self, name, value):
+        """+
+        If the value has a 'name' attribute, it is returned to unmodified.
+        Otherwise the name and the value with any linesep characters removed
+        are passed to the header_factory method, and the resulting custom
+        header object is returned.  Any surrogateescaped bytes get turned
+        into the unicode unknown-character glyph.
+
+        """
+        if hasattr(value, 'name'):
+            return value
+        # We can't use splitlines here because it splits on more than \r and \n.
+        value = ''.join(linesep_splitter.split(value))
+        return self.header_factory(name, value)
+
+    def fold(self, name, value):
+        """+
+        Header folding is controlled by the refold_source policy setting.  A
+        value is considered to be a 'source value' if and only if it does not
+        have a 'name' attribute (having a 'name' attribute means it is a header
+        object of some sort).  If a source value needs to be refolded according
+        to the policy, it is converted into a custom header object by passing
+        the name and the value with any linesep characters removed to the
+        header_factory method.  Folding of a custom header object is done by
+        calling its fold method with the current policy.
+
+        Source values are split into lines using splitlines.  If the value is
+        not to be refolded, the lines are rejoined using the linesep from the
+        policy and returned.  The exception is lines containing non-ascii
+        binary data.  In that case the value is refolded regardless of the
+        refold_source setting, which causes the binary data to be CTE encoded
+        using the unknown-8bit charset.
+
+        """
+        return self._fold(name, value, refold_binary=True)
+
+    def fold_binary(self, name, value):
+        """+
+        The same as fold if cte_type is 7bit, except that the returned value is
+        bytes.
+
+        If cte_type is 8bit, non-ASCII binary data is converted back into
+        bytes.  Headers with binary data are not refolded, regardless of the
+        refold_header setting, since there is no way to know whether the binary
+        data consists of single byte characters or multibyte characters.
+
+        If utf8 is true, headers are encoded to utf8, otherwise to ascii with
+        non-ASCII unicode rendered as encoded words.
+
+        """
+        folded = self._fold(name, value, refold_binary=self.cte_type=='7bit')
+        charset = 'utf8' if self.utf8 else 'ascii'
+        return folded.encode(charset, 'surrogateescape')
+
+    def _fold(self, name, value, refold_binary=False):
+        if hasattr(value, 'name'):
+            return value.fold(policy=self)
+        maxlen = self.max_line_length if self.max_line_length else float('inf')
+        lines = value.splitlines()
+        refold = (self.refold_source == 'all' or
+                  self.refold_source == 'long' and
+                    (lines and len(lines[0])+len(name)+2 > maxlen or
+                     any(len(x) > maxlen for x in lines[1:])))
+        if refold or refold_binary and _has_surrogates(value):
+            return self.header_factory(name, ''.join(lines)).fold(policy=self)
+        return name + ': ' + self.linesep.join(lines) + self.linesep
+
+
+default = EmailPolicy()
+
+# Make the default policy use the class default header_factory
+del default.header_factory
+strict = default.clone(raise_on_defect=True)
+
+SMTP = default.clone(linesep='\r\n')
+
+HTTP = default.clone(linesep='\r\n', max_line_length=None)
+
+SMTPUTF8 = SMTP.clone(utf8=True)
diff --git a/modules/language/python/module/email/utils.py b/modules/language/python/module/email/utils.py
index abe3895..861f1ad 100644
--- a/modules/language/python/module/email/utils.py
+++ b/modules/language/python/module/email/utils.py
@@ -24,6 +24,7 @@ __all__ = [
     '_has_surrogates'
     ]
 
+
 import os
 import re
 import time