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