Fatal error: Uncaught Error: Class "Drupal\Tests\Composer\Plugin\FixturesBase" not found in /home/qcsvlel/www/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Fixtures.php:17 Stack trace: #0 {main} thrown in /home/qcsvlel/www/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Fixtures.php on line 17