Fatal error: Uncaught Error: Class "Drupal\migrate_drupal\Plugin\migrate\field\FieldPluginBase" not found in /home/www/drupal8/test/core/modules/telephone/src/Plugin/migrate/field/d7/PhoneField.php:18 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/telephone/src/Plugin/migrate/field/d7/PhoneField.php on line 18