New PHP deprecation not previously fixed, it seems:
00:01:51.455 1) MediaWiki\Extension\OAuth\Tests\BearerTokenValidatorTest::testValidateAuthorization with data set "wrong scope" ('mw:bad:scope:1000', null)
00:01:51.455 League\OAuth2\Server\Exception\OAuthServerException::__construct(): Implicitly marking parameter $previous as nullable is deprecated, the explicit nullable type must be used instead
00:01:51.455
00:01:51.455 /workspace/src/vendor/league/oauth2-server/src/Exception/OAuthServerException.php:60
00:01:51.455 /workspace/src/extensions/OAuth/src/BearerTokenValidator.php:24
00:01:51.455 /workspace/src/extensions/OAuth/tests/phpunit/BearerTokenValidatorTest.php:50