Fatal error: Uncaught Error: Class "Drupal\Core\Block\BlockBase" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Menu/Plugin/Block/LocalTasksBlock.php:22
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Menu/Plugin/Block/LocalTasksBlock.php on line 22