Warning: Class "\Drupal\Core\TempStore\TempStoreException" not found in /home/www/drupal8/test/core/modules/user/src/PrivateTempStore.php on line 13

Fatal error: Uncaught Error: Class "Drupal\Core\TempStore\PrivateTempStore" not found in /home/www/drupal8/test/core/modules/user/src/PrivateTempStore.php:25 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/user/src/PrivateTempStore.php on line 25