Addresses the ability to show 404 Page Not Found pages from events, that wasn't covered in the D462.

Preparations

In IDE:

1. open the /core/units/users/users_event_handler.php file for editing
2. add protected function OnTestPageNotFound(kEvent $event) { $this->Application->UrlManager->show404(); } code after the \UsersEventHandler::mapPermissions method
3. add the 'OnTestPageNotFound' => array('self' => true), element to the $permissions array of the \UsersEventHandler::mapPermissions method
4. save changes

Test Plan

1. repeat the test plan from the D462
2. open the /platform/page-not-found.html?events[u]=OnTestPageNotFound URL on the Front-End
3. confirm, that you're stayed on the page URL and seeing Page Not Found page