Fatal error: Uncaught Error: Class "Drupal\Core\Plugin\DefaultPluginManager" not found in /home/qcsvlel/www/core/tests/Drupal/Tests/Core/Plugin/TestPluginManager.php:15 Stack trace: #0 {main} thrown in /home/qcsvlel/www/core/tests/Drupal/Tests/Core/Plugin/TestPluginManager.php on line 15