Fatal error: Uncaught Error: Class "OCP\Migration\SimpleMigrationStep" not found in /var/www/html/nextcloud/apps/activity/lib/Migration/Version2010Date20190416112817.php:18 Stack trace: #0 {main} thrown in /var/www/html/nextcloud/apps/activity/lib/Migration/Version2010Date20190416112817.php on line 18