title: Google Cloud Storage auth failure when using boto and gcs-oauth2-boto-plugin
body: <p>I'm following <a href="https://cloud.google.com/storage/docs/gspythonlibrary" rel="nofollow">this</a> tutorial on using boto to access google cloud storage. I created a service account, downloaded the p12 file, and generated the .boto config file using "gsutil config -e" command. However, when I tried to list the buckets in my google cloud storage, I get following error. </p>
  
  <pre><code>import boto
  import gcs_oauth2_boto_plugin
  uri = boto.storage_uri('', 'gs')
  for b in uri.get_all_buckets():
  ...     print b.name
  ... 
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/boto/storage_uri.py", line 571, in get_all_buckets
      return conn.get_all_buckets(headers)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/boto/s3/connection.py", line 436, in get_all_buckets
      response = self.make_request('GET', headers=headers)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/boto/s3/connection.py", line 664, in make_request
      retry_handler=retry_handler
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/boto/connection.py", line 1053, in make_request
      retry_handler=retry_handler)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/boto/connection.py", line 911, in _mexe
      request.authorize(connection=self)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/boto/connection.py", line 375, in authorize
      connection._auth_handler.add_auth(self, **kwargs)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/gcs_oauth2_boto_plugin/oauth2_plugin.py", line 70, in add_auth
      self.oauth2_client.GetAuthorizationHeader()
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/gcs_oauth2_boto_plugin/oauth2_client.py", line 347, in GetAuthorizationHeader
      return 'Bearer %s' % self.GetAccessToken().token
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/gcs_oauth2_boto_plugin/oauth2_client.py", line 318, in GetAccessToken
      access_token = self.FetchAccessToken()
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/gcs_oauth2_boto_plugin/oauth2_client.py", line 395, in FetchAccessToken
      credentials.refresh(http)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/oauth2client/client.py", line 516, in refresh
      self._refresh(http.request)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/oauth2client/client.py", line 653, in _refresh
      self._do_refresh_request(http_request)
    File "/home/deployer/ENV/local/lib/python2.7/site-packages/oauth2client/client.py", line 710, in _do_refresh_request
      raise AccessTokenRefreshError(error_msg)
  oauth2client.client.AccessTokenRefreshError: invalid_grant
  </code></pre>