I got this unrelated error in CI when running the tests for https://gerrit.wikimedia.org/r/c/mediawiki/extensions/DiscussionTools/+/682699:
19:44:16 26 04 2021 17:44:16.179:DEBUG [proxy]: proxying request - /wiki/Special:JavaScriptTest/qunit/export to 127.0.0.1:9412 19:44:16 INFO:backend.PhpWebserver:[Mon Apr 26 17:44:16 2021] PHP Fatal error: Access level to CentralAuthPrimaryAuthenticationProvider::$userNameUtils must be protected (as in class MediaWiki\Auth\AbstractPasswordPrimaryAuthenticationProvider) or weaker in /workspace/src/extensions/CentralAuth/includes/CentralAuthPrimaryAuthenticationProvider.php on line 0 19:44:16 INFO:backend.PhpWebserver:[Mon Apr 26 17:44:16 2021] 127.0.0.1:44588 [200]: /wiki/Special:JavaScriptTest/qunit/export - Access level to CentralAuthPrimaryAuthenticationProvider::$userNameUtils must be protected (as in class MediaWiki\Auth\AbstractPasswordPrimaryAuthenticationProvider) or weaker in /workspace/src/extensions/CentralAuth/includes/CentralAuthPrimaryAuthenticationProvider.php on line 0
This is preventing us from merging changes (unless we override CI).