'``Configuration._deployment_from_config`` raises a
``ConfigurationError`` if the deployment_configuration does not
contain an ``u"nodes"`` key.'

def test_error_on_missing_nodes_key(self):

    exception = self.assertRaises(ConfigurationError, deployment_from_configuration, DeploymentState(), {}, set())
    self.assertEqual(u"Deployment    configuration    has    an    error.    Missing    'nodes'    key.", exception.message)
