'Acquiring a lease on node A if a lease already exits for that dataset
on node B will fail.'

def test_acquire_already_exists_different_node(self):

    d = self.acquire_lease(None)
    d.addCallback((lambda _: self.assertResult('POST', '/configuration/leases', request_body={u'dataset_id': unicode(self.dataset3), u'node_uuid': unicode(self.node2), u'expires': None}, expected_code=CONFLICT, expected_result={u'description': u'Lease    already    held.'})))
    def no_update(_):
        self.assertEqual(self.persistence_service.get().leases[self.dataset3].node_id, self.node3)
    d.addCallback(no_update)
    return d
