**Task:** If at least one mention failed after a save, send the editor a notification including the failure reasons.
**Failure reasons to be covered:**
* user name not found
* Message: Your mention for "UserX" was not sent because the user was not found.
* > 50 mentions
* Message: Your mentions were not sent because they exceeded the limit of 50 mentions at a time.
* anonymous user
* Message: Your mention for 100.200.300 was not sent, because the user is anonymous.
* mention on own page:
* Message: Your mention for "UserY" was not sent because you mentioned him/her on his/her own page.
* message to self:
* Message: Your mention was not sent because it was addressed to yourself.
**Screenshots:**
To come. As a first sneak peak see {F4171034}
**Background:** This task is based on a wish that received 21 points (#9) in the German Community Wishlist[1]. Originally, the wish was to receive an information about the sent messages. To keep the number of notifications smaller, and to help people use mentions in a way that they are sent, the task informs about mention failures, and adds the reasons for the failure as well.
[1] Link to wish (in German): https://de.wikipedia.org/wiki/Wikipedia:Umfragen/Technische_W%C3%BCnsche_2015/Topw%C3%BCnsche#Bei_Speichern_Hinweis_.C3.BCber_abgegebene_Benachrichtigungen_.5BUmfrage_2015.5D
in English: https://meta.wikimedia.org/wiki/WMDE_Technical_Wishes#Notifications_about_failed_mentions