Fatal error: Uncaught Error: Class "Drupal\Core\Command\DbCommandBase" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Command/DbImportCommand.php:20 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Command/DbImportCommand.php on line 20