Fatal error: Uncaught Error: Interface "Drupal\Core\Cache\CacheBackendInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Cache/ChainedFastBackend.php:48 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Cache/ChainedFastBackend.php on line 48