Handle arguments to be passed thru to a subprocess using '--'.

        :returns: tuple of two lists; args and pass-thru-args

def parse_passthru_args(argv):
        """Handle arguments to be passed thru to a subprocess using '--'.

        :returns: tuple of two lists; args and pass-thru-args
        """
        if '--' in argv:
            dashdash = argv.index("--")
            return argv[:dashdash], argv[dashdash + 1:]
        return argv, []