Fatal error: Uncaught Error: Interface "TYPO3\CMS\Core\SingletonInterface" not found in /var/www/html/dev.hallescherfc.de/vendor/b13/container/Classes/Domain/Service/ContainerService.php:20 Stack trace: #0 {main} thrown in /var/www/html/dev.hallescherfc.de/vendor/b13/container/Classes/Domain/Service/ContainerService.php on line 20