subprocess
authorStefan Israelsson Tampe <stefan.itampe@gmail.com>
Sun, 8 Apr 2018 19:30:48 +0000 (21:30 +0200)
committerStefan Israelsson Tampe <stefan.itampe@gmail.com>
Sun, 8 Apr 2018 19:30:48 +0000 (21:30 +0200)
modules/language/python/module/subprocess.py [new file with mode: 0644]

diff --git a/modules/language/python/module/subprocess.py b/modules/language/python/module/subprocess.py
new file mode 100644 (file)
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--- /dev/null
@@ -0,0 +1,1583 @@
+module(subprocess)
+
+r"""Subprocesses with accessible I/O streams
+
+This module allows you to spawn processes, connect to their
+input/output/error pipes, and obtain their return codes.
+
+For a complete description of this module see the Python documentation.
+
+Main API
+========
+run(...): Runs a command, waits for it to complete, then returns a
+          CompletedProcess instance.
+Popen(...): A class for flexibly executing a command in a new process
+
+Constants
+---------
+DEVNULL: Special value that indicates that os.devnull should be used
+PIPE:    Special value that indicates a pipe should be created
+STDOUT:  Special value that indicates that stderr should go to stdout
+
+
+Older API
+=========
+call(...): Runs a command, waits for it to complete, then returns
+    the return code.
+check_call(...): Same as call() but raises CalledProcessError()
+    if return code is not 0
+check_output(...): Same as check_call() but returns the contents of
+    stdout instead of a return code
+getoutput(...): Runs a command in the shell, waits for it to complete,
+    then returns the output
+getstatusoutput(...): Runs a command in the shell, waits for it to complete,
+    then returns a (exitcode, output) tuple
+"""
+
+import sys
+_mswindows = (sys.platform == "win32")
+
+import io
+import os
+import time
+import signal
+import builtins
+import warnings
+import errno
+from time import monotonic as _time
+
+# Exception classes used by this module.
+class SubprocessError(Exception): pass
+
+
+class CalledProcessError(SubprocessError):
+    """Raised when run() is called with check=True and the process
+    returns a non-zero exit status.
+
+    Attributes:
+      cmd, returncode, stdout, stderr, output
+    """
+    def __init__(self, returncode, cmd, output=None, stderr=None):
+        self.returncode = returncode
+        self.cmd = cmd
+        self.output = output
+        self.stderr = stderr
+
+    def __str__(self):
+        if self.returncode and self.returncode < 0:
+            try:
+                return "Command '%s' died with %r." % (
+                        self.cmd, signal.Signals(-self.returncode))
+            except ValueError:
+                return "Command '%s' died with unknown signal %d." % (
+                        self.cmd, -self.returncode)
+        else:
+            return "Command '%s' returned non-zero exit status %d." % (
+                    self.cmd, self.returncode)
+
+    @property
+    def stdout(self):
+        """Alias for output attribute, to match stderr"""
+        return self.output
+
+    @stdout.setter
+    def stdout_setter(self, value):
+        # There's no obvious reason to set this, but allow it anyway so
+        # .stdout is a transparent alias for .output
+        self.output = value
+
+
+class TimeoutExpired(SubprocessError):
+    """This exception is raised when the timeout expires while waiting for a
+    child process.
+
+    Attributes:
+        cmd, output, stdout, stderr, timeout
+    """
+    def __init__(self, cmd, timeout, output=None, stderr=None):
+        self.cmd = cmd
+        self.timeout = timeout
+        self.output = output
+        self.stderr = stderr
+
+    def __str__(self):
+        return ("Command '%s' timed out after %s seconds" %
+                (self.cmd, self.timeout))
+
+    @property
+    def stdout(self):
+        return self.output
+
+    @stdout.setter
+    def stdout_setter(self, value):
+        # There's no obvious reason to set this, but allow it anyway so
+        # .stdout is a transparent alias for .output
+        self.output = value
+
+
+if _mswindows:
+    import threading
+    import msvcrt
+    import _winapi
+    class STARTUPINFO:
+        dwFlags = 0
+        hStdInput = None
+        hStdOutput = None
+        hStdError = None
+        wShowWindow = 0
+else:
+    import _posixsubprocess
+    import select
+    import selectors
+    try:
+        import threading
+    except ImportError:
+        import dummy_threading as threading
+
+    # When select or poll has indicated that the file is writable,
+    # we can write up to _PIPE_BUF bytes without risk of blocking.
+    # POSIX defines PIPE_BUF as >= 512.
+    _PIPE_BUF = getattr(select, 'PIPE_BUF', 512)
+
+    # poll/select have the advantage of not requiring any extra file
+    # descriptor, contrarily to epoll/kqueue (also, they require a single
+    # syscall).
+    if hasattr(selectors, 'PollSelector'):
+        _PopenSelector = selectors.PollSelector
+    else:
+        _PopenSelector = selectors.SelectSelector
+
+
+__all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "getstatusoutput",
+           "getoutput", "check_output", "run", "CalledProcessError", "DEVNULL",
+           "SubprocessError", "TimeoutExpired", "CompletedProcess"]
+           # NOTE: We intentionally exclude list2cmdline as it is
+           # considered an internal implementation detail.  issue10838.
+
+if _mswindows:
+    from _winapi import (CREATE_NEW_CONSOLE, CREATE_NEW_PROCESS_GROUP,
+                         STD_INPUT_HANDLE, STD_OUTPUT_HANDLE,
+                         STD_ERROR_HANDLE, SW_HIDE,
+                         STARTF_USESTDHANDLES, STARTF_USESHOWWINDOW)
+
+    __all__.extend(["CREATE_NEW_CONSOLE", "CREATE_NEW_PROCESS_GROUP",
+                    "STD_INPUT_HANDLE", "STD_OUTPUT_HANDLE",
+                    "STD_ERROR_HANDLE", "SW_HIDE",
+                    "STARTF_USESTDHANDLES", "STARTF_USESHOWWINDOW",
+                    "STARTUPINFO"])
+
+    class Handle(int):
+        closed = False
+
+        def Close(self, CloseHandle=_winapi.CloseHandle):
+            if not self.closed:
+                self.closed = True
+                CloseHandle(self)
+
+        def Detach(self):
+            if not self.closed:
+                self.closed = True
+                return int(self)
+            raise ValueError("already closed")
+
+        def __repr__(self):
+            return "%s(%d)" % (self.__class__.__name__, int(self))
+
+        __del__ = Close
+        __str__ = __repr__
+
+
+# This lists holds Popen instances for which the underlying process had not
+# exited at the time its __del__ method got called: those processes are wait()ed
+# for synchronously from _cleanup() when a new Popen object is created, to avoid
+# zombie processes.
+_active = []
+
+def _cleanup():
+    for inst in _active[:]:
+        res = inst._internal_poll(_deadstate=sys.maxsize)
+        if res is not None:
+            try:
+                _active.remove(inst)
+            except ValueError:
+                # This can happen if two threads create a new Popen instance.
+                # It's harmless that it was already removed, so ignore.
+                pass
+
+PIPE = -1
+STDOUT = -2
+DEVNULL = -3
+
+
+# XXX This function is only used by multiprocessing and the test suite,
+# but it's here so that it can be imported when Python is compiled without
+# threads.
+
+def _optim_args_from_interpreter_flags():
+    """Return a list of command-line arguments reproducing the current
+    optimization settings in sys.flags."""
+    args = []
+    value = sys.flags.optimize
+    if value > 0:
+        args.append('-' + 'O' * value)
+    return args
+
+
+def _args_from_interpreter_flags():
+    """Return a list of command-line arguments reproducing the current
+    settings in sys.flags and sys.warnoptions."""
+    flag_opt_map = {
+        'debug': 'd',
+        # 'inspect': 'i',
+        # 'interactive': 'i',
+        'dont_write_bytecode': 'B',
+        'no_user_site': 's',
+        'no_site': 'S',
+        'ignore_environment': 'E',
+        'verbose': 'v',
+        'bytes_warning': 'b',
+        'quiet': 'q',
+        # -O is handled in _optim_args_from_interpreter_flags()
+    }
+    args = _optim_args_from_interpreter_flags()
+    for flag, opt in flag_opt_map.items():
+        v = getattr(sys.flags, flag)
+        if v > 0:
+            args.append('-' + opt * v)
+    for opt in sys.warnoptions:
+        args.append('-W' + opt)
+    return args
+
+
+def call(*popenargs, timeout=None, **kwargs):
+    """Run command with arguments.  Wait for command to complete or
+    timeout, then return the returncode attribute.
+
+    The arguments are the same as for the Popen constructor.  Example:
+
+    retcode = call(["ls", "-l"])
+    """
+    with Popen(*popenargs, **kwargs) as p:
+        try:
+            return p.wait(timeout=timeout)
+        except:
+            p.kill()
+            p.wait()
+            raise
+
+
+def check_call(*popenargs, **kwargs):
+    """Run command with arguments.  Wait for command to complete.  If
+    the exit code was zero then return, otherwise raise
+    CalledProcessError.  The CalledProcessError object will have the
+    return code in the returncode attribute.
+
+    The arguments are the same as for the call function.  Example:
+
+    check_call(["ls", "-l"])
+    """
+    retcode = call(*popenargs, **kwargs)
+    if retcode:
+        cmd = kwargs.get("args")
+        if cmd is None:
+            cmd = popenargs[0]
+        raise CalledProcessError(retcode, cmd)
+    return 0
+
+
+def check_output(*popenargs, timeout=None, **kwargs):
+    r"""Run command with arguments and return its output.
+
+    If the exit code was non-zero it raises a CalledProcessError.  The
+    CalledProcessError object will have the return code in the returncode
+    attribute and output in the output attribute.
+
+    The arguments are the same as for the Popen constructor.  Example:
+
+    >>> check_output(["ls", "-l", "/dev/null"])
+    b'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null\n'
+
+    The stdout argument is not allowed as it is used internally.
+    To capture standard error in the result, use stderr=STDOUT.
+
+    >>> check_output(["/bin/sh", "-c",
+    ...               "ls -l non_existent_file ; exit 0"],
+    ...              stderr=STDOUT)
+    b'ls: non_existent_file: No such file or directory\n'
+
+    There is an additional optional argument, "input", allowing you to
+    pass a string to the subprocess's stdin.  If you use this argument
+    you may not also use the Popen constructor's "stdin" argument, as
+    it too will be used internally.  Example:
+
+    >>> check_output(["sed", "-e", "s/foo/bar/"],
+    ...              input=b"when in the course of fooman events\n")
+    b'when in the course of barman events\n'
+
+    If universal_newlines=True is passed, the "input" argument must be a
+    string and the return value will be a string rather than bytes.
+    """
+    if 'stdout' in kwargs:
+        raise ValueError('stdout argument not allowed, it will be overridden.')
+
+    if 'input' in kwargs and kwargs['input'] is None:
+        # Explicitly passing input=None was previously equivalent to passing an
+        # empty string. That is maintained here for backwards compatibility.
+        kwargs['input'] = '' if kwargs.get('universal_newlines', False) else b''
+
+    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
+               **kwargs).stdout
+
+
+class CompletedProcess(object):
+    """A process that has finished running.
+
+    This is returned by run().
+
+    Attributes:
+      args: The list or str args passed to run().
+      returncode: The exit code of the process, negative for signals.
+      stdout: The standard output (None if not captured).
+      stderr: The standard error (None if not captured).
+    """
+    def __init__(self, args, returncode, stdout=None, stderr=None):
+        self.args = args
+        self.returncode = returncode
+        self.stdout = stdout
+        self.stderr = stderr
+
+    def __repr__(self):
+        args = ['args={!r}'.format(self.args),
+                'returncode={!r}'.format(self.returncode)]
+        if self.stdout is not None:
+            args.append('stdout={!r}'.format(self.stdout))
+        if self.stderr is not None:
+            args.append('stderr={!r}'.format(self.stderr))
+        return "{}({})".format(type(self).__name__, ', '.join(args))
+
+    def check_returncode(self):
+        """Raise CalledProcessError if the exit code is non-zero."""
+        if self.returncode:
+            raise CalledProcessError(self.returncode, self.args, self.stdout,
+                                     self.stderr)
+
+
+def run(*popenargs, input=None, timeout=None, check=False, **kwargs):
+    """Run command with arguments and return a CompletedProcess instance.
+
+    The returned instance will have attributes args, returncode, stdout and
+    stderr. By default, stdout and stderr are not captured, and those attributes
+    will be None. Pass stdout=PIPE and/or stderr=PIPE in order to capture them.
+
+    If check is True and the exit code was non-zero, it raises a
+    CalledProcessError. The CalledProcessError object will have the return code
+    in the returncode attribute, and output & stderr attributes if those streams
+    were captured.
+
+    If timeout is given, and the process takes too long, a TimeoutExpired
+    exception will be raised.
+
+    There is an optional argument "input", allowing you to
+    pass a string to the subprocess's stdin.  If you use this argument
+    you may not also use the Popen constructor's "stdin" argument, as
+    it will be used internally.
+
+    The other arguments are the same as for the Popen constructor.
+
+    If universal_newlines=True is passed, the "input" argument must be a
+    string and stdout/stderr in the returned object will be strings rather than
+    bytes.
+    """
+    if input is not None:
+        if 'stdin' in kwargs:
+            raise ValueError('stdin and input arguments may not both be used.')
+        kwargs['stdin'] = PIPE
+
+    with Popen(*popenargs, **kwargs) as process:
+        try:
+            stdout, stderr = process.communicate(input, timeout=timeout)
+        except TimeoutExpired:
+            process.kill()
+            stdout, stderr = process.communicate()
+            raise TimeoutExpired(process.args, timeout, output=stdout,
+                                 stderr=stderr)
+        except:
+            process.kill()
+            process.wait()
+            raise
+        retcode = process.poll()
+        if check and retcode:
+            raise CalledProcessError(retcode, process.args,
+                                     output=stdout, stderr=stderr)
+    return CompletedProcess(process.args, retcode, stdout, stderr)
+
+
+def list2cmdline(seq):
+    """
+    Translate a sequence of arguments into a command line
+    string, using the same rules as the MS C runtime:
+
+    1) Arguments are delimited by white space, which is either a
+       space or a tab.
+
+    2) A string surrounded by double quotation marks is
+       interpreted as a single argument, regardless of white space
+       contained within.  A quoted string can be embedded in an
+       argument.
+
+    3) A double quotation mark preceded by a backslash is
+       interpreted as a literal double quotation mark.
+
+    4) Backslashes are interpreted literally, unless they
+       immediately precede a double quotation mark.
+
+    5) If backslashes immediately precede a double quotation mark,
+       every pair of backslashes is interpreted as a literal
+       backslash.  If the number of backslashes is odd, the last
+       backslash escapes the next double quotation mark as
+       described in rule 3.
+    """
+
+    # See
+    # http://msdn.microsoft.com/en-us/library/17w5ykft.aspx
+    # or search http://msdn.microsoft.com for
+    # "Parsing C++ Command-Line Arguments"
+    result = []
+    needquote = False
+    for arg in seq:
+        bs_buf = []
+
+        # Add a space to separate this argument from the others
+        if result:
+            result.append(' ')
+
+        needquote = (" " in arg) or ("\t" in arg) or not arg
+        if needquote:
+            result.append('"')
+
+        for c in arg:
+            if c == '\\':
+                # Don't know if we need to double yet.
+                bs_buf.append(c)
+            elif c == '"':
+                # Double backslashes.
+                result.append('\\' * len(bs_buf)*2)
+                bs_buf = []
+                result.append('\\"')
+            else:
+                # Normal char
+                if bs_buf:
+                    result.extend(bs_buf)
+                    bs_buf = []
+                result.append(c)
+
+        # Add remaining backslashes, if any.
+        if bs_buf:
+            result.extend(bs_buf)
+
+        if needquote:
+            result.extend(bs_buf)
+            result.append('"')
+
+    return ''.join(result)
+
+
+# Various tools for executing commands and looking at their output and status.
+#
+
+def getstatusoutput(cmd):
+    """Return (exitcode, output) of executing cmd in a shell.
+
+    Execute the string 'cmd' in a shell with 'check_output' and
+    return a 2-tuple (status, output). The locale encoding is used
+    to decode the output and process newlines.
+
+    A trailing newline is stripped from the output.
+    The exit status for the command can be interpreted
+    according to the rules for the function 'wait'. Example:
+
+    >>> import subprocess
+    >>> subprocess.getstatusoutput('ls /bin/ls')
+    (0, '/bin/ls')
+    >>> subprocess.getstatusoutput('cat /bin/junk')
+    (1, 'cat: /bin/junk: No such file or directory')
+    >>> subprocess.getstatusoutput('/bin/junk')
+    (127, 'sh: /bin/junk: not found')
+    >>> subprocess.getstatusoutput('/bin/kill $$')
+    (-15, '')
+    """
+    try:
+        data = check_output(cmd, shell=True, universal_newlines=True, stderr=STDOUT)
+        exitcode = 0
+    except CalledProcessError as ex:
+        data = ex.output
+        exitcode = ex.returncode
+    if data[-1:] == '\n':
+        data = data[:-1]
+    return exitcode, data
+
+def getoutput(cmd):
+    """Return output (stdout or stderr) of executing cmd in a shell.
+
+    Like getstatusoutput(), except the exit status is ignored and the return
+    value is a string containing the command's output.  Example:
+
+    >>> import subprocess
+    >>> subprocess.getoutput('ls /bin/ls')
+    '/bin/ls'
+    """
+    return getstatusoutput(cmd)[1]
+
+
+_PLATFORM_DEFAULT_CLOSE_FDS = object()
+
+
+class Popen(object):
+    """ Execute a child program in a new process.
+
+    For a complete description of the arguments see the Python documentation.
+
+    Arguments:
+      args: A string, or a sequence of program arguments.
+
+      bufsize: supplied as the buffering argument to the open() function when
+          creating the stdin/stdout/stderr pipe file objects
+
+      executable: A replacement program to execute.
+
+      stdin, stdout and stderr: These specify the executed programs' standard
+          input, standard output and standard error file handles, respectively.
+
+      preexec_fn: (POSIX only) An object to be called in the child process
+          just before the child is executed.
+
+      close_fds: Controls closing or inheriting of file descriptors.
+
+      shell: If true, the command will be executed through the shell.
+
+      cwd: Sets the current directory before the child is executed.
+
+      env: Defines the environment variables for the new process.
+
+      universal_newlines: If true, use universal line endings for file
+          objects stdin, stdout and stderr.
+
+      startupinfo and creationflags (Windows only)
+
+      restore_signals (POSIX only)
+
+      start_new_session (POSIX only)
+
+      pass_fds (POSIX only)
+
+      encoding and errors: Text mode encoding and error handling to use for
+          file objects stdin, stdout and stderr.
+
+    Attributes:
+        stdin, stdout, stderr, pid, returncode
+    """
+    _child_created = False  # Set here since __del__ checks it
+
+    def __init__(self, args, bufsize=-1, executable=None,
+                 stdin=None, stdout=None, stderr=None,
+                 preexec_fn=None, close_fds=_PLATFORM_DEFAULT_CLOSE_FDS,
+                 shell=False, cwd=None, env=None, universal_newlines=False,
+                 startupinfo=None, creationflags=0,
+                 restore_signals=True, start_new_session=False,
+                 pass_fds=(), *, encoding=None, errors=None):
+        """Create new Popen instance."""
+        _cleanup()
+        # Held while anything is calling waitpid before returncode has been
+        # updated to prevent clobbering returncode if wait() or poll() are
+        # called from multiple threads at once.  After acquiring the lock,
+        # code must re-check self.returncode to see if another thread just
+        # finished a waitpid() call.
+        self._waitpid_lock = threading.Lock()
+
+        self._input = None
+        self._communication_started = False
+        if bufsize is None:
+            bufsize = -1  # Restore default
+        if not isinstance(bufsize, int):
+            raise TypeError("bufsize must be an integer")
+
+        if _mswindows:
+            if preexec_fn is not None:
+                raise ValueError("preexec_fn is not supported on Windows "
+                                 "platforms")
+            any_stdio_set = (stdin is not None or stdout is not None or
+                             stderr is not None)
+            if close_fds is _PLATFORM_DEFAULT_CLOSE_FDS:
+                if any_stdio_set:
+                    close_fds = False
+                else:
+                    close_fds = True
+            elif close_fds and any_stdio_set:
+                raise ValueError(
+                        "close_fds is not supported on Windows platforms"
+                        " if you redirect stdin/stdout/stderr")
+        else:
+            # POSIX
+            if close_fds is _PLATFORM_DEFAULT_CLOSE_FDS:
+                close_fds = True
+            if pass_fds and not close_fds:
+                warnings.warn("pass_fds overriding close_fds.", RuntimeWarning)
+                close_fds = True
+            if startupinfo is not None:
+                raise ValueError("startupinfo is only supported on Windows "
+                                 "platforms")
+            if creationflags != 0:
+                raise ValueError("creationflags is only supported on Windows "
+                                 "platforms")
+
+        self.args = args
+        self.stdin = None
+        self.stdout = None
+        self.stderr = None
+        self.pid = None
+        self.returncode = None
+        self.universal_newlines = universal_newlines
+        self.encoding = encoding
+        self.errors = errors
+
+        # Input and output objects. The general principle is like
+        # this:
+        #
+        # Parent                   Child
+        # ------                   -----
+        # p2cwrite   ---stdin--->  p2cread
+        # c2pread    <--stdout---  c2pwrite
+        # errread    <--stderr---  errwrite
+        #
+        # On POSIX, the child objects are file descriptors.  On
+        # Windows, these are Windows file handles.  The parent objects
+        # are file descriptors on both platforms.  The parent objects
+        # are -1 when not using PIPEs. The child objects are -1
+        # when not redirecting.
+
+        (p2cread, p2cwrite,
+         c2pread, c2pwrite,
+         errread, errwrite) = self._get_handles(stdin, stdout, stderr)
+
+        # We wrap OS handles *before* launching the child, otherwise a
+        # quickly terminating child could make our fds unwrappable
+        # (see #8458).
+
+        if _mswindows:
+            if p2cwrite != -1:
+                p2cwrite = msvcrt.open_osfhandle(p2cwrite.Detach(), 0)
+            if c2pread != -1:
+                c2pread = msvcrt.open_osfhandle(c2pread.Detach(), 0)
+            if errread != -1:
+                errread = msvcrt.open_osfhandle(errread.Detach(), 0)
+
+        text_mode = encoding or errors or universal_newlines
+
+        self._closed_child_pipe_fds = False
+
+        try:
+            if p2cwrite != -1:
+                self.stdin = io.open(p2cwrite, 'wb', bufsize)
+                if text_mode:
+                    self.stdin = io.TextIOWrapper(self.stdin, write_through=True,
+                            line_buffering=(bufsize == 1),
+                            encoding=encoding, errors=errors)
+            if c2pread != -1:
+                self.stdout = io.open(c2pread, 'rb', bufsize)
+                if text_mode:
+                    self.stdout = io.TextIOWrapper(self.stdout,
+                            encoding=encoding, errors=errors)
+            if errread != -1:
+                self.stderr = io.open(errread, 'rb', bufsize)
+                if text_mode:
+                    self.stderr = io.TextIOWrapper(self.stderr,
+                            encoding=encoding, errors=errors)
+
+            self._execute_child(args, executable, preexec_fn, close_fds,
+                                pass_fds, cwd, env,
+                                startupinfo, creationflags, shell,
+                                p2cread, p2cwrite,
+                                c2pread, c2pwrite,
+                                errread, errwrite,
+                                restore_signals, start_new_session)
+        except:
+            # Cleanup if the child failed starting.
+            for f in filter(None, (self.stdin, self.stdout, self.stderr)):
+                try:
+                    f.close()
+                except OSError:
+                    pass  # Ignore EBADF or other errors.
+
+            if not self._closed_child_pipe_fds:
+                to_close = []
+                if stdin == PIPE:
+                    to_close.append(p2cread)
+                if stdout == PIPE:
+                    to_close.append(c2pwrite)
+                if stderr == PIPE:
+                    to_close.append(errwrite)
+                if hasattr(self, '_devnull'):
+                    to_close.append(self._devnull)
+                for fd in to_close:
+                    try:
+                        if _mswindows and isinstance(fd, Handle):
+                            fd.Close()
+                        else:
+                            os.close(fd)
+                    except OSError:
+                        pass
+
+            raise
+
+    def _translate_newlines(self, data, encoding, errors):
+        data = data.decode(encoding, errors)
+        return data.replace("\r\n", "\n").replace("\r", "\n")
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type, value, traceback):
+        if self.stdout:
+            self.stdout.close()
+        if self.stderr:
+            self.stderr.close()
+        try:  # Flushing a BufferedWriter may raise an error
+            if self.stdin:
+                self.stdin.close()
+        finally:
+            # Wait for the process to terminate, to avoid zombies.
+            self.wait()
+
+    def __del__(self, _maxsize=sys.maxsize, _warn=warnings.warn):
+        if not self._child_created:
+            # We didn't get to successfully create a child process.
+            return
+        if self.returncode is None:
+            # Not reading subprocess exit status creates a zombi process which
+            # is only destroyed at the parent python process exit
+            _warn("subprocess %s is still running" % self.pid,
+                  ResourceWarning, source=self)
+        # In case the child hasn't been waited on, check if it's done.
+        self._internal_poll(_deadstate=_maxsize)
+        if self.returncode is None and _active is not None:
+            # Child is still running, keep us alive until we can wait on it.
+            _active.append(self)
+
+    def _get_devnull(self):
+        if not hasattr(self, '_devnull'):
+            self._devnull = os.open(os.devnull, os.O_RDWR)
+        return self._devnull
+
+    def _stdin_write(self, input):
+        if input:
+            try:
+                self.stdin.write(input)
+            except BrokenPipeError:
+                pass  # communicate() must ignore broken pipe errors.
+            except OSError as exc:
+                if exc.errno == errno.EINVAL:
+                    # bpo-19612, bpo-30418: On Windows, stdin.write() fails
+                    # with EINVAL if the child process exited or if the child
+                    # process is still running but closed the pipe.
+                    pass
+                else:
+                    raise
+
+        try:
+            self.stdin.close()
+        except BrokenPipeError:
+            pass  # communicate() must ignore broken pipe errors.
+        except OSError as exc:
+            if exc.errno == errno.EINVAL:
+                pass
+            else:
+                raise
+
+    def communicate(self, input=None, timeout=None):
+        """Interact with process: Send data to stdin.  Read data from
+        stdout and stderr, until end-of-file is reached.  Wait for
+        process to terminate.
+
+        The optional "input" argument should be data to be sent to the
+        child process (if self.universal_newlines is True, this should
+        be a string; if it is False, "input" should be bytes), or
+        None, if no data should be sent to the child.
+
+        communicate() returns a tuple (stdout, stderr).  These will be
+        bytes or, if self.universal_newlines was True, a string.
+        """
+
+        if self._communication_started and input:
+            raise ValueError("Cannot send input after starting communication")
+
+        # Optimization: If we are not worried about timeouts, we haven't
+        # started communicating, and we have one or zero pipes, using select()
+        # or threads is unnecessary.
+        if (timeout is None and not self._communication_started and
+            [self.stdin, self.stdout, self.stderr].count(None) >= 2):
+            stdout = None
+            stderr = None
+            if self.stdin:
+                self._stdin_write(input)
+            elif self.stdout:
+                stdout = self.stdout.read()
+                self.stdout.close()
+            elif self.stderr:
+                stderr = self.stderr.read()
+                self.stderr.close()
+            self.wait()
+        else:
+            if timeout is not None:
+                endtime = _time() + timeout
+            else:
+                endtime = None
+
+            try:
+                stdout, stderr = self._communicate(input, endtime, timeout)
+            finally:
+                self._communication_started = True
+
+            sts = self.wait(timeout=self._remaining_time(endtime))
+
+        return (stdout, stderr)
+
+
+    def poll(self):
+        """Check if child process has terminated. Set and return returncode
+        attribute."""
+        return self._internal_poll()
+
+
+    def _remaining_time(self, endtime):
+        """Convenience for _communicate when computing timeouts."""
+        if endtime is None:
+            return None
+        else:
+            return endtime - _time()
+
+
+    def _check_timeout(self, endtime, orig_timeout):
+        """Convenience for checking if a timeout has expired."""
+        if endtime is None:
+            return
+        if _time() > endtime:
+            raise TimeoutExpired(self.args, orig_timeout)
+
+
+    if _mswindows:
+        #
+        # Windows methods
+        #
+        def _get_handles(self, stdin, stdout, stderr):
+            """Construct and return tuple with IO objects:
+            p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
+            """
+            if stdin is None and stdout is None and stderr is None:
+                return (-1, -1, -1, -1, -1, -1)
+
+            p2cread, p2cwrite = -1, -1
+            c2pread, c2pwrite = -1, -1
+            errread, errwrite = -1, -1
+
+            if stdin is None:
+                p2cread = _winapi.GetStdHandle(_winapi.STD_INPUT_HANDLE)
+                if p2cread is None:
+                    p2cread, _ = _winapi.CreatePipe(None, 0)
+                    p2cread = Handle(p2cread)
+                    _winapi.CloseHandle(_)
+            elif stdin == PIPE:
+                p2cread, p2cwrite = _winapi.CreatePipe(None, 0)
+                p2cread, p2cwrite = Handle(p2cread), Handle(p2cwrite)
+            elif stdin == DEVNULL:
+                p2cread = msvcrt.get_osfhandle(self._get_devnull())
+            elif isinstance(stdin, int):
+                p2cread = msvcrt.get_osfhandle(stdin)
+            else:
+                # Assuming file-like object
+                p2cread = msvcrt.get_osfhandle(stdin.fileno())
+            p2cread = self._make_inheritable(p2cread)
+
+            if stdout is None:
+                c2pwrite = _winapi.GetStdHandle(_winapi.STD_OUTPUT_HANDLE)
+                if c2pwrite is None:
+                    _, c2pwrite = _winapi.CreatePipe(None, 0)
+                    c2pwrite = Handle(c2pwrite)
+                    _winapi.CloseHandle(_)
+            elif stdout == PIPE:
+                c2pread, c2pwrite = _winapi.CreatePipe(None, 0)
+                c2pread, c2pwrite = Handle(c2pread), Handle(c2pwrite)
+            elif stdout == DEVNULL:
+                c2pwrite = msvcrt.get_osfhandle(self._get_devnull())
+            elif isinstance(stdout, int):
+                c2pwrite = msvcrt.get_osfhandle(stdout)
+            else:
+                # Assuming file-like object
+                c2pwrite = msvcrt.get_osfhandle(stdout.fileno())
+            c2pwrite = self._make_inheritable(c2pwrite)
+
+            if stderr is None:
+                errwrite = _winapi.GetStdHandle(_winapi.STD_ERROR_HANDLE)
+                if errwrite is None:
+                    _, errwrite = _winapi.CreatePipe(None, 0)
+                    errwrite = Handle(errwrite)
+                    _winapi.CloseHandle(_)
+            elif stderr == PIPE:
+                errread, errwrite = _winapi.CreatePipe(None, 0)
+                errread, errwrite = Handle(errread), Handle(errwrite)
+            elif stderr == STDOUT:
+                errwrite = c2pwrite
+            elif stderr == DEVNULL:
+                errwrite = msvcrt.get_osfhandle(self._get_devnull())
+            elif isinstance(stderr, int):
+                errwrite = msvcrt.get_osfhandle(stderr)
+            else:
+                # Assuming file-like object
+                errwrite = msvcrt.get_osfhandle(stderr.fileno())
+            errwrite = self._make_inheritable(errwrite)
+
+            return (p2cread, p2cwrite,
+                    c2pread, c2pwrite,
+                    errread, errwrite)
+
+
+        def _make_inheritable(self, handle):
+            """Return a duplicate of handle, which is inheritable"""
+            h = _winapi.DuplicateHandle(
+                _winapi.GetCurrentProcess(), handle,
+                _winapi.GetCurrentProcess(), 0, 1,
+                _winapi.DUPLICATE_SAME_ACCESS)
+            return Handle(h)
+
+
+        def _execute_child(self, args, executable, preexec_fn, close_fds,
+                           pass_fds, cwd, env,
+                           startupinfo, creationflags, shell,
+                           p2cread, p2cwrite,
+                           c2pread, c2pwrite,
+                           errread, errwrite,
+                           unused_restore_signals, unused_start_new_session):
+            """Execute program (MS Windows version)"""
+
+            assert not pass_fds, "pass_fds not supported on Windows."
+
+            if not isinstance(args, str):
+                args = list2cmdline(args)
+
+            # Process startup details
+            if startupinfo is None:
+                startupinfo = STARTUPINFO()
+            if -1 not in (p2cread, c2pwrite, errwrite):
+                startupinfo.dwFlags |= _winapi.STARTF_USESTDHANDLES
+                startupinfo.hStdInput = p2cread
+                startupinfo.hStdOutput = c2pwrite
+                startupinfo.hStdError = errwrite
+
+            if shell:
+                startupinfo.dwFlags |= _winapi.STARTF_USESHOWWINDOW
+                startupinfo.wShowWindow = _winapi.SW_HIDE
+                comspec = os.environ.get("COMSPEC", "cmd.exe")
+                args = '{} /c "{}"'.format (comspec, args)
+
+            # Start the process
+            try:
+                hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
+                                         # no special security
+                                         None, None,
+                                         int(not close_fds),
+                                         creationflags,
+                                         env,
+                                         os.fspath(cwd) if cwd is not None else None,
+                                         startupinfo)
+            finally:
+                # Child is launched. Close the parent's copy of those pipe
+                # handles that only the child should have open.  You need
+                # to make sure that no handles to the write end of the
+                # output pipe are maintained in this process or else the
+                # pipe will not close when the child process exits and the
+                # ReadFile will hang.
+                if p2cread != -1:
+                    p2cread.Close()
+                if c2pwrite != -1:
+                    c2pwrite.Close()
+                if errwrite != -1:
+                    errwrite.Close()
+                if hasattr(self, '_devnull'):
+                    os.close(self._devnull)
+                # Prevent a double close of these handles/fds from __init__
+                # on error.
+                self._closed_child_pipe_fds = True
+
+            # Retain the process handle, but close the thread handle
+            self._child_created = True
+            self._handle = Handle(hp)
+            self.pid = pid
+            _winapi.CloseHandle(ht)
+
+        def _internal_poll(self, _deadstate=None,
+                _WaitForSingleObject=_winapi.WaitForSingleObject,
+                _WAIT_OBJECT_0=_winapi.WAIT_OBJECT_0,
+                _GetExitCodeProcess=_winapi.GetExitCodeProcess):
+            """Check if child process has terminated.  Returns returncode
+            attribute.
+
+            This method is called by __del__, so it can only refer to objects
+            in its local scope.
+
+            """
+            if self.returncode is None:
+                if _WaitForSingleObject(self._handle, 0) == _WAIT_OBJECT_0:
+                    self.returncode = _GetExitCodeProcess(self._handle)
+            return self.returncode
+
+
+        def wait(self, timeout=None, endtime=None):
+            """Wait for child process to terminate.  Returns returncode
+            attribute."""
+            if endtime is not None:
+                warnings.warn(
+                    "'endtime' argument is deprecated; use 'timeout'.",
+                    DeprecationWarning,
+                    stacklevel=2)
+                timeout = self._remaining_time(endtime)
+            if timeout is None:
+                timeout_millis = _winapi.INFINITE
+            else:
+                timeout_millis = int(timeout * 1000)
+            if self.returncode is None:
+                result = _winapi.WaitForSingleObject(self._handle,
+                                                    timeout_millis)
+                if result == _winapi.WAIT_TIMEOUT:
+                    raise TimeoutExpired(self.args, timeout)
+                self.returncode = _winapi.GetExitCodeProcess(self._handle)
+            return self.returncode
+
+
+        def _readerthread(self, fh, buffer):
+            buffer.append(fh.read())
+            fh.close()
+
+
+        def _communicate(self, input, endtime, orig_timeout):
+            # Start reader threads feeding into a list hanging off of this
+            # object, unless they've already been started.
+            if self.stdout and not hasattr(self, "_stdout_buff"):
+                self._stdout_buff = []
+                self.stdout_thread = \
+                        threading.Thread(target=self._readerthread,
+                                         args=(self.stdout, self._stdout_buff))
+                self.stdout_thread.daemon = True
+                self.stdout_thread.start()
+            if self.stderr and not hasattr(self, "_stderr_buff"):
+                self._stderr_buff = []
+                self.stderr_thread = \
+                        threading.Thread(target=self._readerthread,
+                                         args=(self.stderr, self._stderr_buff))
+                self.stderr_thread.daemon = True
+                self.stderr_thread.start()
+
+            if self.stdin:
+                self._stdin_write(input)
+
+            # Wait for the reader threads, or time out.  If we time out, the
+            # threads remain reading and the fds left open in case the user
+            # calls communicate again.
+            if self.stdout is not None:
+                self.stdout_thread.join(self._remaining_time(endtime))
+                if self.stdout_thread.is_alive():
+                    raise TimeoutExpired(self.args, orig_timeout)
+            if self.stderr is not None:
+                self.stderr_thread.join(self._remaining_time(endtime))
+                if self.stderr_thread.is_alive():
+                    raise TimeoutExpired(self.args, orig_timeout)
+
+            # Collect the output from and close both pipes, now that we know
+            # both have been read successfully.
+            stdout = None
+            stderr = None
+            if self.stdout:
+                stdout = self._stdout_buff
+                self.stdout.close()
+            if self.stderr:
+                stderr = self._stderr_buff
+                self.stderr.close()
+
+            # All data exchanged.  Translate lists into strings.
+            if stdout is not None:
+                stdout = stdout[0]
+            if stderr is not None:
+                stderr = stderr[0]
+
+            return (stdout, stderr)
+
+        def send_signal(self, sig):
+            """Send a signal to the process."""
+            # Don't signal a process that we know has already died.
+            if self.returncode is not None:
+                return
+            if sig == signal.SIGTERM:
+                self.terminate()
+            elif sig == signal.CTRL_C_EVENT:
+                os.kill(self.pid, signal.CTRL_C_EVENT)
+            elif sig == signal.CTRL_BREAK_EVENT:
+                os.kill(self.pid, signal.CTRL_BREAK_EVENT)
+            else:
+                raise ValueError("Unsupported signal: {}".format(sig))
+
+        def terminate(self):
+            """Terminates the process."""
+            # Don't terminate a process that we know has already died.
+            if self.returncode is not None:
+                return
+            try:
+                _winapi.TerminateProcess(self._handle, 1)
+            except PermissionError:
+                # ERROR_ACCESS_DENIED (winerror 5) is received when the
+                # process already died.
+                rc = _winapi.GetExitCodeProcess(self._handle)
+                if rc == _winapi.STILL_ACTIVE:
+                    raise
+                self.returncode = rc
+
+        kill = terminate
+
+    else:
+        #
+        # POSIX methods
+        #
+        def _get_handles(self, stdin, stdout, stderr):
+            """Construct and return tuple with IO objects:
+            p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
+            """
+            p2cread, p2cwrite = -1, -1
+            c2pread, c2pwrite = -1, -1
+            errread, errwrite = -1, -1
+
+            if stdin is None:
+                pass
+            elif stdin == PIPE:
+                p2cread, p2cwrite = os.pipe()
+            elif stdin == DEVNULL:
+                p2cread = self._get_devnull()
+            elif isinstance(stdin, int):
+                p2cread = stdin
+            else:
+                # Assuming file-like object
+                p2cread = stdin.fileno()
+
+            if stdout is None:
+                pass
+            elif stdout == PIPE:
+                c2pread, c2pwrite = os.pipe()
+            elif stdout == DEVNULL:
+                c2pwrite = self._get_devnull()
+            elif isinstance(stdout, int):
+                c2pwrite = stdout
+            else:
+                # Assuming file-like object
+                c2pwrite = stdout.fileno()
+
+            if stderr is None:
+                pass
+            elif stderr == PIPE:
+                errread, errwrite = os.pipe()
+            elif stderr == STDOUT:
+                if c2pwrite != -1:
+                    errwrite = c2pwrite
+                else: # child's stdout is not set, use parent's stdout
+                    errwrite = sys.__stdout__.fileno()
+            elif stderr == DEVNULL:
+                errwrite = self._get_devnull()
+            elif isinstance(stderr, int):
+                errwrite = stderr
+            else:
+                # Assuming file-like object
+                errwrite = stderr.fileno()
+
+            return (p2cread, p2cwrite,
+                    c2pread, c2pwrite,
+                    errread, errwrite)
+
+
+        def _execute_child(self, args, executable, preexec_fn, close_fds,
+                           pass_fds, cwd, env,
+                           startupinfo, creationflags, shell,
+                           p2cread, p2cwrite,
+                           c2pread, c2pwrite,
+                           errread, errwrite,
+                           restore_signals, start_new_session):
+            """Execute program (POSIX version)"""
+
+            if isinstance(args, (str, bytes)):
+                args = [args]
+            else:
+                args = list(args)
+
+            if shell:
+                args = ["/bin/sh", "-c"] + args
+                if executable:
+                    args[0] = executable
+
+            if executable is None:
+                executable = args[0]
+            orig_executable = executable
+
+            # For transferring possible exec failure from child to parent.
+            # Data format: "exception name:hex errno:description"
+            # Pickle is not used; it is complex and involves memory allocation.
+            errpipe_read, errpipe_write = os.pipe()
+            # errpipe_write must not be in the standard io 0, 1, or 2 fd range.
+            low_fds_to_close = []
+            while errpipe_write < 3:
+                low_fds_to_close.append(errpipe_write)
+                errpipe_write = os.dup(errpipe_write)
+            for low_fd in low_fds_to_close:
+                os.close(low_fd)
+            try:
+                try:
+                    # We must avoid complex work that could involve
+                    # malloc or free in the child process to avoid
+                    # potential deadlocks, thus we do all this here.
+                    # and pass it to fork_exec()
+
+                    if env is not None:
+                        env_list = []
+                        for k, v in env.items():
+                            k = os.fsencode(k)
+                            if b'=' in k:
+                                raise ValueError("illegal environment variable name")
+                            env_list.append(k + b'=' + os.fsencode(v))
+                    else:
+                        env_list = None  # Use execv instead of execve.
+                    executable = os.fsencode(executable)
+                    if os.path.dirname(executable):
+                        executable_list = (executable,)
+                    else:
+                        # This matches the behavior of os._execvpe().
+                        executable_list = tuple(
+                            os.path.join(os.fsencode(dir), executable)
+                            for dir in os.get_exec_path(env))
+                    fds_to_keep = set(pass_fds)
+                    fds_to_keep.add(errpipe_write)
+                    self.pid = _posixsubprocess.fork_exec(
+                            args, executable_list,
+                            close_fds, tuple(sorted(map(int, fds_to_keep))),
+                            cwd, env_list,
+                            p2cread, p2cwrite, c2pread, c2pwrite,
+                            errread, errwrite,
+                            errpipe_read, errpipe_write,
+                            restore_signals, start_new_session, preexec_fn)
+                    self._child_created = True
+                finally:
+                    # be sure the FD is closed no matter what
+                    os.close(errpipe_write)
+
+                # self._devnull is not always defined.
+                devnull_fd = getattr(self, '_devnull', None)
+                if p2cread != -1 and p2cwrite != -1 and p2cread != devnull_fd:
+                    os.close(p2cread)
+                if c2pwrite != -1 and c2pread != -1 and c2pwrite != devnull_fd:
+                    os.close(c2pwrite)
+                if errwrite != -1 and errread != -1 and errwrite != devnull_fd:
+                    os.close(errwrite)
+                if devnull_fd is not None:
+                    os.close(devnull_fd)
+                # Prevent a double close of these fds from __init__ on error.
+                self._closed_child_pipe_fds = True
+
+                # Wait for exec to fail or succeed; possibly raising an
+                # exception (limited in size)
+                errpipe_data = bytearray()
+                while True:
+                    part = os.read(errpipe_read, 50000)
+                    errpipe_data += part
+                    if not part or len(errpipe_data) > 50000:
+                        break
+            finally:
+                # be sure the FD is closed no matter what
+                os.close(errpipe_read)
+
+            if errpipe_data:
+                try:
+                    pid, sts = os.waitpid(self.pid, 0)
+                    if pid == self.pid:
+                        self._handle_exitstatus(sts)
+                    else:
+                        self.returncode = sys.maxsize
+                except ChildProcessError:
+                    pass
+
+                try:
+                    exception_name, hex_errno, err_msg = (
+                            errpipe_data.split(b':', 2))
+                    # The encoding here should match the encoding
+                    # written in by the subprocess implementations
+                    # like _posixsubprocess
+                    err_msg = err_msg.decode()
+                except ValueError:
+                    exception_name = b'SubprocessError'
+                    hex_errno = b'0'
+                    err_msg = 'Bad exception data from child: {!r}'.format(
+                                  bytes(errpipe_data))
+                child_exception_type = getattr(
+                        builtins, exception_name.decode('ascii'),
+                        SubprocessError)
+                if issubclass(child_exception_type, OSError) and hex_errno:
+                    errno_num = int(hex_errno, 16)
+                    child_exec_never_called = (err_msg == "noexec")
+                    if child_exec_never_called:
+                        err_msg = ""
+                        # The error must be from chdir(cwd).
+                        err_filename = cwd
+                    else:
+                        err_filename = orig_executable
+                    if errno_num != 0:
+                        err_msg = os.strerror(errno_num)
+                        if errno_num == errno.ENOENT:
+                            err_msg += ': ' + repr(err_filename)
+                    raise child_exception_type(errno_num, err_msg, err_filename)
+                raise child_exception_type(err_msg)
+
+
+        def _handle_exitstatus(self, sts, _WIFSIGNALED=os.WIFSIGNALED,
+                _WTERMSIG=os.WTERMSIG, _WIFEXITED=os.WIFEXITED,
+                _WEXITSTATUS=os.WEXITSTATUS, _WIFSTOPPED=os.WIFSTOPPED,
+                _WSTOPSIG=os.WSTOPSIG):
+            """All callers to this function MUST hold self._waitpid_lock."""
+            # This method is called (indirectly) by __del__, so it cannot
+            # refer to anything outside of its local scope.
+            if _WIFSIGNALED(sts):
+                self.returncode = -_WTERMSIG(sts)
+            elif _WIFEXITED(sts):
+                self.returncode = _WEXITSTATUS(sts)
+            elif _WIFSTOPPED(sts):
+                self.returncode = -_WSTOPSIG(sts)
+            else:
+                # Should never happen
+                raise SubprocessError("Unknown child exit status!")
+
+
+        def _internal_poll(self, _deadstate=None, _waitpid=os.waitpid,
+                _WNOHANG=os.WNOHANG, _ECHILD=errno.ECHILD):
+            """Check if child process has terminated.  Returns returncode
+            attribute.
+
+            This method is called by __del__, so it cannot reference anything
+            outside of the local scope (nor can any methods it calls).
+
+            """
+            if self.returncode is None:
+                if not self._waitpid_lock.acquire(False):
+                    # Something else is busy calling waitpid.  Don't allow two
+                    # at once.  We know nothing yet.
+                    return None
+                try:
+                    if self.returncode is not None:
+                        return self.returncode  # Another thread waited.
+                    pid, sts = _waitpid(self.pid, _WNOHANG)
+                    if pid == self.pid:
+                        self._handle_exitstatus(sts)
+                except OSError as e:
+                    if _deadstate is not None:
+                        self.returncode = _deadstate
+                    elif e.errno == _ECHILD:
+                        # This happens if SIGCLD is set to be ignored or
+                        # waiting for child processes has otherwise been
+                        # disabled for our process.  This child is dead, we
+                        # can't get the status.
+                        # http://bugs.python.org/issue15756
+                        self.returncode = 0
+                finally:
+                    self._waitpid_lock.release()
+            return self.returncode
+
+
+        def _try_wait(self, wait_flags):
+            """All callers to this function MUST hold self._waitpid_lock."""
+            try:
+                (pid, sts) = os.waitpid(self.pid, wait_flags)
+            except ChildProcessError:
+                # This happens if SIGCLD is set to be ignored or waiting
+                # for child processes has otherwise been disabled for our
+                # process.  This child is dead, we can't get the status.
+                pid = self.pid
+                sts = 0
+            return (pid, sts)
+
+
+        def wait(self, timeout=None, endtime=None):
+            """Wait for child process to terminate.  Returns returncode
+            attribute."""
+            if self.returncode is not None:
+                return self.returncode
+
+            if endtime is not None:
+                warnings.warn(
+                    "'endtime' argument is deprecated; use 'timeout'.",
+                    DeprecationWarning,
+                    stacklevel=2)
+            if endtime is not None or timeout is not None:
+                if endtime is None:
+                    endtime = _time() + timeout
+                elif timeout is None:
+                    timeout = self._remaining_time(endtime)
+
+            if endtime is not None:
+                # Enter a busy loop if we have a timeout.  This busy loop was
+                # cribbed from Lib/threading.py in Thread.wait() at r71065.
+                delay = 0.0005 # 500 us -> initial delay of 1 ms
+                while True:
+                    if self._waitpid_lock.acquire(False):
+                        try:
+                            if self.returncode is not None:
+                                break  # Another thread waited.
+                            (pid, sts) = self._try_wait(os.WNOHANG)
+                            assert pid == self.pid or pid == 0
+                            if pid == self.pid:
+                                self._handle_exitstatus(sts)
+                                break
+                        finally:
+                            self._waitpid_lock.release()
+                    remaining = self._remaining_time(endtime)
+                    if remaining <= 0:
+                        raise TimeoutExpired(self.args, timeout)
+                    delay = min(delay * 2, remaining, .05)
+                    time.sleep(delay)
+            else:
+                while self.returncode is None:
+                    with self._waitpid_lock:
+                        if self.returncode is not None:
+                            break  # Another thread waited.
+                        (pid, sts) = self._try_wait(0)
+                        # Check the pid and loop as waitpid has been known to
+                        # return 0 even without WNOHANG in odd situations.
+                        # http://bugs.python.org/issue14396.
+                        if pid == self.pid:
+                            self._handle_exitstatus(sts)
+            return self.returncode
+
+
+        def _communicate(self, input, endtime, orig_timeout):
+            if self.stdin and not self._communication_started:
+                # Flush stdio buffer.  This might block, if the user has
+                # been writing to .stdin in an uncontrolled fashion.
+                try:
+                    self.stdin.flush()
+                except BrokenPipeError:
+                    pass  # communicate() must ignore BrokenPipeError.
+                if not input:
+                    try:
+                        self.stdin.close()
+                    except BrokenPipeError:
+                        pass  # communicate() must ignore BrokenPipeError.
+
+            stdout = None
+            stderr = None
+
+            # Only create this mapping if we haven't already.
+            if not self._communication_started:
+                self._fileobj2output = {}
+                if self.stdout:
+                    self._fileobj2output[self.stdout] = []
+                if self.stderr:
+                    self._fileobj2output[self.stderr] = []
+
+            if self.stdout:
+                stdout = self._fileobj2output[self.stdout]
+            if self.stderr:
+                stderr = self._fileobj2output[self.stderr]
+
+            self._save_input(input)
+
+            if self._input:
+                input_view = memoryview(self._input)
+
+            with _PopenSelector() as selector:
+                if self.stdin and input:
+                    selector.register(self.stdin, selectors.EVENT_WRITE)
+                if self.stdout:
+                    selector.register(self.stdout, selectors.EVENT_READ)
+                if self.stderr:
+                    selector.register(self.stderr, selectors.EVENT_READ)
+
+                while selector.get_map():
+                    timeout = self._remaining_time(endtime)
+                    if timeout is not None and timeout < 0:
+                        raise TimeoutExpired(self.args, orig_timeout)
+
+                    ready = selector.select(timeout)
+                    self._check_timeout(endtime, orig_timeout)
+
+                    # XXX Rewrite these to use non-blocking I/O on the file
+                    # objects; they are no longer using C stdio!
+
+                    for key, events in ready:
+                        if key.fileobj is self.stdin:
+                            chunk = input_view[self._input_offset :
+                                               self._input_offset + _PIPE_BUF]
+                            try:
+                                self._input_offset += os.write(key.fd, chunk)
+                            except BrokenPipeError:
+                                selector.unregister(key.fileobj)
+                                key.fileobj.close()
+                            else:
+                                if self._input_offset >= len(self._input):
+                                    selector.unregister(key.fileobj)
+                                    key.fileobj.close()
+                        elif key.fileobj in (self.stdout, self.stderr):
+                            data = os.read(key.fd, 32768)
+                            if not data:
+                                selector.unregister(key.fileobj)
+                                key.fileobj.close()
+                            self._fileobj2output[key.fileobj].append(data)
+
+            self.wait(timeout=self._remaining_time(endtime))
+
+            # All data exchanged.  Translate lists into strings.
+            if stdout is not None:
+                stdout = b''.join(stdout)
+            if stderr is not None:
+                stderr = b''.join(stderr)
+
+            # Translate newlines, if requested.
+            # This also turns bytes into strings.
+            if self.encoding or self.errors or self.universal_newlines:
+                if stdout is not None:
+                    stdout = self._translate_newlines(stdout,
+                                                      self.stdout.encoding,
+                                                      self.stdout.errors)
+                if stderr is not None:
+                    stderr = self._translate_newlines(stderr,
+                                                      self.stderr.encoding,
+                                                      self.stderr.errors)
+
+            return (stdout, stderr)
+
+
+        def _save_input(self, input):
+            # This method is called from the _communicate_with_*() methods
+            # so that if we time out while communicating, we can continue
+            # sending input if we retry.
+            if self.stdin and self._input is None:
+                self._input_offset = 0
+                self._input = input
+                if input is not None and (
+                    self.encoding or self.errors or self.universal_newlines):
+                    self._input = self._input.encode(self.stdin.encoding,
+                                                     self.stdin.errors)
+
+
+        def send_signal(self, sig):
+            """Send a signal to the process."""
+            # Skip signalling a process that we know has already died.
+            if self.returncode is None:
+                os.kill(self.pid, sig)
+
+        def terminate(self):
+            """Terminate the process with SIGTERM
+            """
+            self.send_signal(signal.SIGTERM)
+
+        def kill(self):
+            """Kill the process with SIGKILL
+            """
+            self.send_signal(signal.SIGKILL)