I have installed tacker server and client using both of their stable/mitaka branches as I'm using openstack mitaka. However, after completing installation I'm checking if it is installed correctly by using command: tacker ext-list When the request goes to server, following error is shown in server log:

2017-03-21 06:11:11.351 12713 ERROR oslo_middleware.catch_errors [-] An error occurred during processing the request: GET /v1.0/extensions.json HTTP/1.0
    Accept: application/json
    Accept-Encoding: gzip, deflate
    Connection: keep-alive
    Content-Type: text/plain
    Host: 127.0.0.1:8888
    User-Agent: python-tackerclient
    X-Auth-Token: e913008b64814ceeb7de7edba80d5c2c
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors Traceback (most recent call last):
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/oslo_middleware/catch_errors.py", line 38, in __call__
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     response = req.get_response(self.application)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1317, in send
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     application, catch_exc_info=False)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1281, in call_application
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     app_iter = application(self.environ, start_response)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 130, in __call__
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     resp = self.call_func(req, *args, **self.kwargs)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 195, in call_func
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     return self.func(req, *args, **kwargs)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/keystonemiddleware/auth_token/__init__.py", line 464, in __call__
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     response = self.process_request(req)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/keystonemiddleware/auth_token/__init__.py", line 732, in process_request
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     resp = super(AuthProtocol, self).process_request(request)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/keystonemiddleware/auth_token/__init__.py", line 492, in process_request
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     data, user_auth_ref = self._do_fetch_token(request.user_token)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/keystonemiddleware/auth_token/__init__.py", line 531, in _do_fetch_token
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     data = self.fetch_token(token)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/keystonemiddleware/auth_token/__init__.py", line 847, in fetch_token
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors     data = self._identity_server.verify_token(token)
    2017-03-21 06:11:11.351 12713 TRACE oslo_middleware.catch_errors   File "/usr/lib/python2.7/dist-packages/keystonemiddleware/auth_token/_identity.py", line 214, in verify_token
    2017-03-21 06 ...