Hmm, not sure why I thought I needed `inline code formatting`. It's all monospace anyway!

Anyway, I'm thinking that adding this somewhere in argparse.py:

class _WrappedIO(object):
    def __init__(self, fileobj):
        self._file = fileobj

    def __exit__(tp, val, tb):
        return True

    def __getattr__(self, name):
        return self._file.__gettattr__(name)

and then applying the attached patch *may* fix this.