def _script_callback_option_parser(option, opt_str, value, parser):
    """
    Store a script's URL or path along to its attribute 'defer', 'async' or None
    """
    attr = ('defer' in opt_str and 'defer' or 'async' in opt_str and
        'async' or None)
    parser.values.script = parser.values.script or []
    parser.values.script.append((value, attr))
    return
