Fatal error: Uncaught Error: Class "Drupal\Tests\BrowserTestBase" not found in /home/www/drupal8/test/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php:42 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php on line 42