Supplement a proper `prog` keyword argument for the subprocessor.
        The superclass technique for getting the `prog` value breaks because
        of our VT100 escape codes injected by `format_help`.

def add_subparsers(self, prog=None, **kwargs):
        """ Supplement a proper `prog` keyword argument for the subprocessor.
        The superclass technique for getting the `prog` value breaks because
        of our VT100 escape codes injected by `format_help`. """
        if prog is None:
            # Use a non-shellish help formatter to avoid vt100 codes.
            f = argparse.HelpFormatter(prog=self.prog)
            f.add_usage(self.usage, self._get_positional_actions(),
                        self._mutually_exclusive_groups, '')
            prog = f.format_help().strip()
        return super().add_subparsers(prog=prog, **kwargs)