Use default php logger channel

How can I test this? It seems the registered logger is actually never used because ErrorHandler::handleException() and ErrorHandler::handleError() are never called (probably because Drupal's error handler catches the error first then provides it to KernelEventSubscriber::onException()).

And I tried installing the monolog module and I can see the exceptions and PHP errors logged by monolog even without this patch.

OK now I get why this is useful.
Without it, trigger_error('foo', E_USER_ERROR); is logged but trigger_error('foo', E_USER_DEPRECATED); is not.
With the patch, they are both logged.

Automatically closed - issue fixed for 2 weeks with no activity.