@dario.crespi.wmit reported that, after upgrade, it was no longer possible to register new users in wiki.wikimedia.it. This was the internal exception:

undefined constant WatchedItem::IGNORE_USER_RIGHTS

It seems it was caused by a very old custom hook in our LocalSettings.php, probably designed to automatically add some pages in the watchlist as default.

The snippet was relying on:

$user->addWatch( $titolo, WatchedItem::IGNORE_USER_RIGHTS );

For now as workaround we have disabled the whole snippet. Then we could fix it, or drop it forever.