Argparse's wrapping behavior is determined by the formatter_class:

http://docs.python.org/library/argparse.html#formatter-class

Is it reasonable to assume that if you're wrapping your own messages you're already specifying formatter_class=argparse.RawTextHelpFormatter? If so, then perhaps the message should be printed via something like:

    formatter = parser._get_formatter()
    formatter.add_text(self.message)
    file.write(formatter.format_help())

This is what we do in _VersionAction, so I guess it's probably what we should do here.