Fatal error: Uncaught Error: Class "OCP\Migration\SimpleMigrationStep" not found in /var/www/html/nextcloud/apps/activity/lib/Migration/Version2011Date20201207091915.php:16 Stack trace: #0 {main} thrown in /var/www/html/nextcloud/apps/activity/lib/Migration/Version2011Date20201207091915.php on line 16