def _format_rule_default_json(default):
    """Create a json node from policy.RuleDefault or policy.DocumentedRuleDefault.

    :param default: A policy.RuleDefault or policy.DocumentedRuleDefault object
    :returns: A string containing a json representation of the RuleDefault
    """
    return '"%(name)s": "%(check_str)s"' % {'name': default.name,
        'check_str': default.check_str}
