'Test that cyclical extends in the config raises an exception'

def test_cyclical_extends(self):

    try:
        self.get_custom_config(**{'c2_extends': 'c3', 'c3_extends': 'c2'})
        self.get_custom_config(**{'c2_extends': 'c3', 'c3_extends': 'c4', 'c4_extends': 'c2'})
    except exception.ConfigError:
        pass
    else:
        raise Exception('config    allows    cyclical    extends    graph')
