'If the era<->node mapping is available, return the node UUID.'

def test_known_era(self):

    node_uuid = uuid4()
    era = uuid4()
    self.cluster_state_service.apply_changes([UpdateNodeStateEra(era=era, uuid=node_uuid)])
    return self.assertResultItems('GET', ('/state/nodes/by_era/' + bytes(era)), None, OK, {u'uuid': unicode(node_uuid)})
