content: """
  A replacement wrapper around the subprocess module, with a number of
  work-arounds:
  - Provides the check_output function (which subprocess only provides from Python
    2.7 onwards).
  - Provides a stub implementation of subprocess members on Google App Engine
    (which are missing in subprocess).
  
  Instead of importing subprocess, other modules should use this as follows:
  
  from matplotlib.compat import subprocess
  
  This module is safe to import from anywhere within matplotlib.
  """
  
  from __future__ import absolute_import    # Required to import subprocess
  from __future__ import print_function
  
  import subprocess
  
  __all__ = ['Popen', 'PIPE', 'STDOUT', 'check_output', 'CalledProcessError']
  
  
  if hasattr(subprocess, 'Popen'):
      Popen = subprocess.Popen
      # Assume that it also has the other constants.
      PIPE = subprocess.PIPE
      STDOUT = subprocess.STDOUT
      CalledProcessError = subprocess.CalledProcessError
  else:
      # In restricted environments (such as Google App Engine), these are
      # non-existent. Replace them with dummy versions that always raise OSError.
      def Popen(*args, **kwargs):
          raise OSError("subprocess.Popen is not supported")
      PIPE = -1
      STDOUT = -2
      # There is no need to catch CalledProcessError. These stubs cannot raise
      # it. None in an except clause will simply not match any exceptions.
      CalledProcessError = None
  
  
  def _check_output(*popenargs, **kwargs):
      r"""Run command with arguments and return its output as a byte
      string.
  
      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"])
      '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)
      'ls: non_existent_file: No such file or directory\n'
      """
      if 'stdout' in kwargs:
          raise ValueError('stdout argument not allowed, it will be overridden.')
      process = Popen(stdout=PIPE, *popenargs, **kwargs)
      output, unused_err = process.communicate()
      retcode = process.poll()
      if retcode:
          cmd = kwargs.get("args")
          if cmd is None:
              cmd = popenargs[0]
          raise subprocess.CalledProcessError(retcode, cmd, output=output)
      return output
  
  
  # python2.7's subprocess provides a check_output method
  if hasattr(subprocess, 'check_output'):
      check_output = subprocess.check_output
  else:
      check_output = _check_output
  