Fatal error: Uncaught Error: Class "Drupal\Core\Ajax\InsertCommand" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Ajax/ReplaceCommand.php:20 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Ajax/ReplaceCommand.php on line 20