Splitting from {T338213} for visibility:
>>! In T338213#8909770, @abi_ wrote:
> On translatewiki.net we had the following error pop up when running the `rebuildLocalisationCache` script:
>
> ```
> [891c19fc2a4c905abf364b8d] [no req] Error: Class 'PSExtensionHandler' not found
> Backtrace:
> from /srv/mediawiki/workdir/extensions/PageForms/includes/PF_PageSchemas.php(15)
> #0 /srv/mediawiki/workdir/includes/AutoLoader.php(222): require()
> #1 [internal function]: AutoLoader::autoload()
> #2 [internal function]: spl_autoload_call()
> #3 /srv/mediawiki/workdir/includes/HookContainer/HookContainer.php(344): is_callable()
> #4 /srv/mediawiki/workdir/includes/HookContainer/HookContainer.php(521): MediaWiki\HookContainer\HookContainer->normalizeHandler()
> #5 /srv/mediawiki/workdir/includes/HookContainer/HookContainer.php(450): MediaWiki\HookContainer\HookContainer->getHandlers()
> #6 /srv/mediawiki/workdir/extensions/SemanticMediaWiki/src/MediaWiki/Hooks.php(152): MediaWiki\HookContainer\HookContainer->register()
> #7 /srv/mediawiki/workdir/extensions/SemanticMediaWiki/src/Setup.php(389): SMW\MediaWiki\Hooks->register()
> #8 /srv/mediawiki/workdir/extensions/SemanticMediaWiki/src/Setup.php(152): SMW\Setup->registerHooks()
> #9 /srv/mediawiki/workdir/extensions/SemanticMediaWiki/includes/SemanticMediaWiki.php(84): SMW\Setup->init()
> #10 /srv/mediawiki/workdir/includes/Setup.php(564): SemanticMediaWiki::onExtensionFunction()
> #11 /srv/mediawiki/workdir/maintenance/run.php(49): require_once(string)
> #12 {main}
> ```
>
> Reverting this change fixed the issue:
>
> [mediawiki/core@master] Simplify HookContainer (v2)
> https://gerrit.wikimedia.org/r/927596
It seems some change is now causing autoloading of a hooks class to trigger, which then causes a fatal because it is extending a class that isn't availalab.e