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