Fatal error: Uncaught Error: Class "Drupal\views\Plugin\views\field\FieldPluginBase" not found in /home/www/drupal8/test/core/modules/user/src/Plugin/views/field/UserData.php:21 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/user/src/Plugin/views/field/UserData.php on line 21