Fatal error: Uncaught Error: Class "Drupal\forum\Plugin\Block\ForumBlockBase" not found in /home/www/drupal8/test/core/modules/forum/src/Plugin/Block/NewTopicsBlock.php:14
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/modules/forum/src/Plugin/Block/NewTopicsBlock.php on line 14