title: oauth2client.client.AccessTokenRefreshError: invalid_grant Only in Docker
body: <p>I have the same code with the same p12 file (checked md5 sums), same account_email, and same scope working on a number of computers, but not working in Docker containers on any of the working computers. My code snippet is as follows:</p>
  
  <pre><code>with open(self.pkcs12_file_path, 'rb') as f:
      key = f.read()
      scope = ['https://www.googleapis.com/auth/bigquery',
               'https://www.googleapis.com/auth/cloud-platform']
      credentials = SignedJwtAssertionCredentials(self.account_email,
                                                      key, scope)
  http = httplib2.Http()
  self.http = credentials.authorize(self.http)
  service = discovery.build('bigquery', 'v2', http=self.http)
  </code></pre>
  
  <p>Whenever I try this inside of a Docker container, I get <code>oauth2client.client.AccessTokenRefreshError: invalid_grant</code> at the <code>discovery.build</code> line. I'm thinking it might have something to do with needing to expose ports, but have no idea which I'd need to expose, or if that's the actual problem. Anyone have any ideas?</p>