Fatal error: Uncaught Error: Class "Drupal\migrate_drupal\Plugin\migrate\cckfield\CckFieldPluginBase" not found in /home/www/drupal8/test/core/modules/file/src/Plugin/migrate/cckfield/d6/FileField.php:24 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/file/src/Plugin/migrate/cckfield/d6/FileField.php on line 24