Fatal error: Uncaught Error: Interface "Drupal\Core\Layout\Icon\IconBuilderInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Layout/Icon/SvgIconBuilder.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Layout/Icon/SvgIconBuilder.php on line 10