traceback example

AttributeError: 'NoneType' object has no attribute 'pool'
  File "oslo_messaging/rpc/server.py", line 165, in _process_incoming
    res = self.dispatcher.dispatch(message)
  File "oslo_messaging/rpc/dispatcher.py", line 309, in dispatch
    return self._do_dispatch(endpoint, method, ctxt, args)
  File "oslo_messaging/rpc/dispatcher.py", line 229, in _do_dispatch
    result = func(ctxt, **new_args)
  File "octavia/controller/queue/v1/endpoints.py", line 122, in batch_update_members
    self.worker.batch_update_members(
  File "__init__.py", line 333, in wrapped_f
    return self(f, *args, **kw)
  File "__init__.py", line 423, in __call__
    do = self.iter(retry_state=retry_state)
  File "__init__.py", line 360, in iter
    return fut.result()
  File "concurrent/futures/_base.py", line 437, in result
    return self.__get_result()
  File "concurrent/futures/_base.py", line 389, in __get_result
    raise self._exception
  File "__init__.py", line 426, in __call__
    result = fn(*args, **kwargs)
  File "octavia/controller/worker/v1/controller_worker.py", line 506, in batch_update_members
    pool = old_members[0].pool