Fatal error: Uncaught Error: Class "Drupal\migrate\Plugin\migrate\destination\EntityContentBase" not found in /home/www/drupal8/test/core/modules/book/src/Plugin/migrate/destination/Book.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/book/src/Plugin/migrate/destination/Book.php on line 15