Bug report:
When you’re joining to a group through the Pilot applications feature, if the Leader of the group has you in his Ignore list, you get an invalid message shown (text string - placeholder).
There should be a proper description instead. I am proposing the example here. Thank you, TheDarkMatter [ESB], for helping me discover this bug.
Example: An error has occurred while joining a group. You’re being ignored by the user.
Screenshot:

Logs: (Check time stamp at 15:33 or 03:33 PM)
[2017.06.30 14.27.37.zip](< base_url >/applications/core/interface/file/attachment.php?id=14760)