Tests broke after upgrade to oslo.config 3.8

After oslo.config was upgradet to version 3.8.0 some of CI tests fail with the following traceback:

Traceback (most recent call last):
2016-02-23 00:44:26.635 | File "/home/jenkins/workspace/gate-murano-python27/murano/tests/unit/api/v1/test_env_templates.py", line 490, in test_create_env_with_template_no_services
2016-02-23 00:44:26.635 | result = req.get_response(self.api)
2016-02-23 00:44:26.635 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/webob/request.py", line 1317, in send
2016-02-23 00:44:26.635 | application, catch_exc_info=False)
2016-02-23 00:44:26.635 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/webob/request.py", line 1281, in call_application
2016-02-23 00:44:26.635 | app_iter = application(self.environ, start_response)
2016-02-23 00:44:26.635 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/webob/dec.py", line 144, in __call__
2016-02-23 00:44:26.635 | return resp(environ, start_response)
2016-02-23 00:44:26.635 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/routes/middleware.py", line 136, in __call__
2016-02-23 00:44:26.636 | response = self.app(environ, start_response)
2016-02-23 00:44:26.636 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/webob/dec.py", line 144, in __call__
2016-02-23 00:44:26.636 | return resp(environ, start_response)
2016-02-23 00:44:26.636 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/webob/dec.py", line 130, in __call__
2016-02-23 00:44:26.636 | resp = self.call_func(req, *args, **self.kwargs)
2016-02-23 00:44:26.636 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/webob/dec.py", line 195, in call_func
2016-02-23 00:44:26.636 | return self.func(req, *args, **kwargs)
2016-02-23 00:44:26.636 | File "murano/common/wsgi.py", line 413, in __call__
2016-02-23 00:44:26.636 | action_result = self.execute_action(action, request, **action_args)
2016-02-23 00:44:26.636 | File "murano/common/wsgi.py", line 428, in execute_action
2016-02-23 00:44:26.636 | return self.dispatch(self.controller, action, request, **action_args)
2016-02-23 00:44:26.636 | File "murano/common/wsgi.py", line 437, in dispatch
2016-02-23 00:44:26.637 | return method(*args, **kwargs)
2016-02-23 00:44:26.637 | File "murano/api/v1/request_statistics.py", line 57, in wrap
2016-02-23 00:44:26.637 | result = func(*args, **kwargs)
2016-02-23 00:44:26.637 | File "murano/api/v1/templates.py", line 196, in create_environment
2016-02-23 00:44:26.637 | body.copy(), request.context)
2016-02-23 00:44:26.637 | File "murano/db/services/environments.py", line 105, in create
2016-02-23 00:44:26.637 | network_driver)
2016-02-23 00:44:26.637 | File "murano/db/services/environments.py", line 210, in generate_default_networks
2016-02-23 00:44:26.637 | CONF.networking.network_config_file)
2016-02-23 00:44:26.637 | File "/home/jenkins/workspace/gate-murano-python27/.tox/py27/local/lib/python2.7/site-packages/oslo_config/cfg.py", line 2479, in find_file
2016-02-23 00:44:26.637 | if self._namespace._config_dirs:
2016-02-23 00:44:26.638 | AttributeError: 'NoneType' object has no attribute '_config_dirs'