Fatal error: Uncaught Error: Class 'WP_Upgrader' not found in /home/qwerasd1234/public_html/tom-test/wp-admin/includes/class-plugin-upgrader.php:21 Stack trace: #0 {main} thrown in /home/qwerasd1234/public_html/tom-test/wp-admin/includes/class-plugin-upgrader.php on line 21