Fatal error: Uncaught Error: Interface "TYPO3\CMS\Core\SingletonInterface" not found in /home/rcmch/test.m-s-i.ch/vendor/typo3/cms-extensionmanager/Classes/Utility/ListUtility.php:41 Stack trace: #0 {main} thrown in /home/rcmch/test.m-s-i.ch/vendor/typo3/cms-extensionmanager/Classes/Utility/ListUtility.php on line 41