Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/eventlet/queue.py", line 117, in switch
    self.greenlet.switch(value)
  File "/usr/lib/python2.7/site-packages/eventlet/greenthread.py", line 214, in main
    result = function(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/oslo_service/service.py", line 643, in run_service
    service.start()
  File "/opt/openstack/nova/nova/service.py", line 158, in start
    self.manager.init_host()
  File "/opt/openstack/nova/nova/compute/manager.py", line 1269, in init_host
    context, self.host, expected_attrs=['info_cache'])
  File "/usr/lib/python2.7/site-packages/oslo_versionedobjects/base.py", line 167, in wrapper
    args, kwargs)
  File "/opt/openstack/nova/nova/conductor/rpcapi.py", line 243, in object_class_action
    objver=objver, args=args, kwargs=kwargs)
  File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/client.py", line 158, in call
    retry=self.retry)
  File "/usr/lib/python2.7/site-packages/oslo_messaging/transport.py", line 90, in _send
    timeout=timeout, retry=retry)
  File "/usr/lib/python2.7/site-packages/oslo_messaging/_drivers/amqpdriver.py", line 431, in send
    retry=retry)
  File "/usr/lib/python2.7/site-packages/oslo_messaging/_drivers/amqpdriver.py", line 422, in _send
    raise result
RemoteError: Remote error: IncompatibleObjectVersion Version 1.20 of InstanceList is not supported. The maximum supported version is: 1.19
[u'Traceback (most recent call last):\n', u'  File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 142, in _dispatch_and_reply\n    executor_callback))\n', u'  File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 186, in _dispatch\n    executor_callback)\n', u'  File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 129, in _do_dispatch\n    result = func(ctxt, **new_args)\n', u'  File "/opt/openstack/nova/nova/conductor/manager.py", line 445, in object_class_action\n    objver)\n', u'  File "/opt/openstack/nova/nova/objects/base.py", line 235, in obj_class_from_name\n    supported=latest_ver)\n', u'IncompatibleObjectVersion: Version 1.20 of InstanceList is not supported. The maximum supported version is: 1.19\n'].