def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def check_bad_url_raises(value):
    try:
        inputs.url(value)
        assert False, "shouldn't get here"
    except ValueError as e:
        assert_equal(six.text_type(e), u"{0} is not a valid URL".format(value))