Fatal error: Uncaught Error: Class "Drupal\Core\KeyValueStore\StorageBase" not found in /home/www/drupal8/test/core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php:16 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php on line 16