Fatal error: Uncaught Error: Class "Drupal\Core\Cache\Context\UserCacheContextBase" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Cache/Context/UserRolesCacheContext.php:17 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Cache/Context/UserRolesCacheContext.php on line 17