Change user events tutorial Redis error to be an inline box

Fixes #1653

endpoints/realtime.py

@@ -99,6 +99,8 @@ def user_test():
 @require_session_login
 def user_subscribe():
   def wrapper(listener):
+    yield 'data: %s\n\n' % json.dumps({})
+
     for event_id, data in listener.event_stream():
       message = {'event': event_id, 'data': data}
       json_string = json.dumps(message)