Fatal error: Uncaught Error: Class "Symfony\Component\Console\Command\Command" not found in /home/www/drupal8/test/core/tests/Drupal/TestSite/Commands/TestSiteTearDownCommand.php:20 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/tests/Drupal/TestSite/Commands/TestSiteTearDownCommand.php on line 20