[ticket/17542] Throw an exception at the exit_handler instead

PHPBB-17542

tests/mock/event_dispatcher.php

@@ -26,9 +26,10 @@ class phpbb_mock_event_dispatcher extends \phpbb\event\dispatcher
 	{
 		$data = (array) $data;
 
+		// Throw an exception if we reach the core's exit_handler()
 		if ($eventName === 'core.exit_handler')
 		{
-			$data['exit_handler_override'] = true;
+			throw new \RuntimeException('Exit handler called');
 		}
 
 		return $data;