Fatal error: Uncaught Error: Class "Drupal\file\FileUsage\FileUsageBase" not found in /home/www/drupal8/test/core/modules/file/src/FileUsage/DatabaseFileUsageBackend.php:12 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/file/src/FileUsage/DatabaseFileUsageBackend.php on line 12