Handle user events Redis not working in tutorial

Also does some basic restyling

Fixes #1586

endpoints/realtime.py

@@ -7,6 +7,7 @@ from auth.auth import require_session_login
 from endpoints.common import route_show_if
 from app import app, userevents
 from auth.permissions import SuperUserPermission
+from data.userevent import CannotReadUserEventsException
 
 import features
 import psutil
@@ -107,5 +108,9 @@ def user_subscribe():
   if not events:
     abort(404)
 
-  listener = userevents.get_listener(current_user.db_user().username, events)
+  try:
+    listener = userevents.get_listener(current_user.db_user().username, events)
+  except CannotReadUserEventsException:
+    abort(504)
+
   return Response(wrapper(listener), mimetype="text/event-stream")