Fatal error: Uncaught Error: Interface "Drupal\Core\Authentication\AuthenticationProviderInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Authentication/AuthenticationManager.php:18 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Authentication/AuthenticationManager.php on line 18