Fatal error: Uncaught Error: Class "Drupal\Core\Ajax\InsertCommand" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Ajax/HtmlCommand.php:19
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Ajax/HtmlCommand.php on line 19