old_contents: import os
  from tempfile import SpooledTemporaryFile
  from contextlib import contextmanager
  
  @contextmanager
  def redirect_stream(output_stream, destination):
      """
      Redirect anything written to ``output_stream`` (typically ``sys.stdin`` or
      ``sys.stdout``) to ``destination`` for the duration of this context.
  
      ``destination`` must provide a ``write()`` method.
      """
      old_stream = os.dup(output_stream.fileno())
      with SpooledTemporaryFile() as s:
          os.dup2(s.fileno(), output_stream.fileno())
          yield
          s.seek(0)
          destination.write(s.read())
      os.dup2(old_stream, output_stream.fileno())
  
new_contents: import os
  from tempfile import SpooledTemporaryFile
  from contextlib import contextmanager
  
  @contextmanager
  def redirect_stream(output_stream, destination):
      """
      Redirect anything written to ``output_stream`` (typically ``sys.stdin`` or
      ``sys.stdout``) to ``destination`` for the duration of this context.
  
      ``destination`` must provide a ``write()`` method.
      """
      while not isinstance(output_stream, file):
          # Looks like this is an XUnit Tee object. Try and find the "real"
          # stderr in its history.
          output_stream = output_stream._streams[-1]
  
      old_stream = os.dup(output_stream.fileno())
      with SpooledTemporaryFile() as s:
          os.dup2(s.fileno(), output_stream.fileno())
          yield
          s.seek(0)
          destination.write(s.read())
      os.dup2(old_stream, output_stream.fileno())
  
subject: Work around XUnit assumptions about streams.