With Contributors and ContributorsAddons extensions installed, Special:UserLogin triggers an error:
Error from line 11 of extensions/ContributorsAddon/ContributorsAddonHooks.php: Call to undefined method Contributors::getNormalList()
The method has been removed from the Contributors extension via 797468db000225acea8fcfc9fabb8c3b57b57128 (for T139879 by @Devirk ). Apparently in favor of a TablePager ( ContributorsTablePager ) which handles the formatting.
Maybe ContributorsAddons is not used anywhere and should be archived instead?
One can reproduce by commenting check experimental on a Gerrit change. For example with the dummy change https://gerrit.wikimedia.org/r/#/c/435975/ . The job quibble-vendor-mysql-php70-docker fails and shows the errors on the web server side:
00:04:01.166 INFO:backend.DevWebServer:[Tue May 29 09:33:03 2018] PHP Fatal error: Uncaught Error: Call to undefined method Contributors::getNormalList() in /workspace/src/extensions/ContributorsAddon/ContributorsAddonHooks.php:11