Noticed when namespacing MediaWiki-extensions-Newsletter....
I can't do
'user-locators' => [ [ EchoNewsletterUserLocator::class, 'locateNewsletterSubscribedUsers' ], ],
BlueSpice does
'user-locators' => [ static::class . '::getSysops' ]
so I've had to do...
'user-locators' => [ [ EchoNewsletterUserLocator::class . '::locateNewsletterSubscribedUsers' ], ],
Which feels hacky...