ironicclient got AttributeError after a long time run

[Zhenzan Zhou]

An ironicclient session was created to poll data from ironic service. After a long time run, the token was expired, it's expected to get HTTPUnauthorized exception, but it raised AttributeError.

WARNING ironicclient.common.http [-] Request returned failure status.
[-] Datasource driver raised exception
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/congress/datasources/datasource_driver.py", line 931, in poll
    self.update_from_datasource() # sets self.state
  File "/usr/local/lib/python2.7/dist-packages/congress/datasources/ironic_driver.py", line 164, in update_from_datasource
    detail=True, limit=0)
  File "/usr/local/lib/python2.7/dist-packages/ironicclient/v1/chassis.py", line 79, in list
    limit=limit)
  File "/usr/local/lib/python2.7/dist-packages/ironicclient/common/base.py", line 96, in _list_pagination
    resp, body = self.api.json_request('GET', url)
  File "/usr/local/lib/python2.7/dist-packages/ironicclient/common/http.py", line 195, in json_request
    resp, body_iter = self._http_request(url, method, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/ironicclient/common/http.py", line 178, in _http_request
    error_json.get('debuginfo'), method, url)
  File "/usr/local/lib/python2.7/dist-packages/ironicclient/exc.py", line 61, in from_response
    return exceptions.from_response(response, message, url)
  File "/usr/local/lib/python2.7/dist-packages/ironicclient/openstack/common/apiclient/exceptions.py", line 450, in from_response
    kwargs["details"] = response.text
AttributeError: HTTPResponse instance has no attribute 'text'