Fatal error: Uncaught Error: Class "Drupal\Core\Plugin\DefaultPluginManager" not found in /home/www/drupal8/test/core/modules/tour/src/TipPluginManager.php:17
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/modules/tour/src/TipPluginManager.php on line 17