The request does not contain the _account on exception pages (403/404)

+++ b/core/lib/Drupal/Core/Controller/ExceptionController.phpundefined
@@ -92,6 +92,7 @@ public function on403Html(FlattenException $exception, Request $request) {
+      $subrequest->attributes->set('_account', $request->attributes->get('_account'));

@@ -165,6 +166,7 @@ public function on404Html(FlattenException $exception, Request $request) {
+      $subrequest->attributes->set('_account', $request->attributes->get('_account'));

As everything with an underscore is kind of special (_account, _system_path) i am wondering whether we should copy all of them.

Just a rough patch so other people can work on it.

Let's combine them.

Adding tag. I will work on some tests

Opened a pull request to make it easier to add additonal parameters, see https://github.com/symfony/symfony/pull/8716

Here is a test.
For some odd reason I had to hack the error log in order to not fail due to a thrown exception.

See #2062151: Create a current user service to ensure that current account is always available

The approach used here can't work anymore, as we should rather rely on the current_user service.

The current_user service should totally solve the problem described in the issue, so we can close this now.

Thanks for bringing that issue up again.