This is what we get in oxauth.log when visiting the URL:
2015-12-03 09:46:25,646 TRACE [org.xdi.oxauth.service.SessionIdService] Found session_id cookie: '97e7b1ce-5815-4e48-aaec-ce85dd19f798'
2015-12-03 09:46:25,648 TRACE [org.xdi.oxauth.auth.AuthenticationFilter] Process Session Auth, sessionId = 97e7b1ce-5815-4e48-aaec-ce85dd19f798, requireAuth = true
2015-12-03 09:46:25,648 DEBUG [org.xdi.oxauth.model.error.ErrorResponseFactory] Looking for the error with id: invalid_client
2015-12-03 09:46:25,648 DEBUG [org.xdi.oxauth.model.error.ErrorResponseFactory] Found error, id: invalid_client