'``Configuration._parse_environment_config`` returns ``None``
if passed an application config that does not include an
``environment`` key.'

def test_environment_variables_none_if_missing(self):

    config = {u'mysql-hybridcluster': {u'image': u'flocker/mysql'}}
    parser = FlockerConfiguration(config)
    self.assertIsNone(parser._parse_environment_config(u'mysql-hybridcluster', config))
