Fatal error: Uncaught Error: Class "WP_Upgrader_Skin" not found in /var/www/andovercg/staging/wp-admin/includes/class-automatic-upgrader-skin.php:21
Stack trace:
#0 {main}
thrown in /var/www/andovercg/staging/wp-admin/includes/class-automatic-upgrader-skin.php on line 21