Fatal error: Uncaught Error: Class "WP_Upgrader_Skin" not found in C:\xampp\htdocs\wordpress\wp-admin\includes\class-language-pack-upgrader-skin.php:18 Stack trace: #0 {main} thrown in C:\xampp\htdocs\wordpress\wp-admin\includes\class-language-pack-upgrader-skin.php on line 18