Can you create a minimal example application that allows to reproduce your issue?

Related to #27516? This was a BC break that has been reverted (see l linked issue.)

https://github.com/dominikzogg/symfony-bug-hunting/pull/1

@nicolas-grekas seems so, cause i had the error after removing some bundles (twig and security are two of them)

This means you should fix your code I suppose, "not a bug"...

@nicolas-grekas well, i used a original standard edition for demo, dropped twig, and this means all kernel exceptions need to catch by ourself?

Yes, that's always been the case except in a few 3.4/4.0 versions but that introduced a BC break. You need to register an exception listener (what TwigBundle does) or to catch the exception yourself.

Can you explain me, what http exception handling has to do with twig?

TwigBundle, not Twig only. See https://github.com/symfony/symfony/blob/2.8/src/Symfony/Bundle/TwigBundle/Resources/config/twig.xml#L140

I have the same issue after upgrading from 3.4.11 to 3.4.12. When pages were not found it generated a nice standard error page (https://www.dropbox.com/s/udevmgjwra0p4zf/Screenshot%202018-06-27%2022.12.27.png?dl=0) but now an 500 Internal Server error is returned and the logs show

[critical] Uncaught Exception: Unable to find the controller for path "/non_existing". The route is wrongly configured.

Yep, sorry about that. This behavior might be reintroduced but as a new feature on 4.2 (see #27519) and with an implementation that doesn't break BC.

You can register an exception listener instead by the way.