Fatal error: Uncaught Error: Class "Drupal\Core\Menu\LocalTaskDefault" not found in /home/www/drupal8/test/core/modules/tracker/src/Plugin/Menu/UserTrackerTab.php:11 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/tracker/src/Plugin/Menu/UserTrackerTab.php on line 11