Throw error if oauth listener does not start.

src/librssguard/network-web/oauth2service.cpp

@@ -266,6 +266,11 @@ bool OAuth2Service::login() {
   if (!m_redirectionHandler->isListening()) {
     qCriticalNN << LOGSEC_OAUTH
                 << "Cannot log-in because OAuth redirection handler is not listening.";
+
+    emit tokensRetrieveError(QString(), tr("Failed to starting OAuth "
+                                           "redirection listener. Maybe your "
+                                           "rights are not high enough."));
+
     return false;
   }