Fatal error: Uncaught Error: Class "Drupal\Core\Lock\LockBackendAbstract" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Lock/DatabaseLockBackend.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Lock/DatabaseLockBackend.php on line 15