[PhpUnitBridge] weak vendors mode silence legitimate deprecations #21991

Not sure if that's the expected behaviour, but say if you have a test requesting a private service, you should get a warning along the lines of:

Requesting the "PrivateFoo" private service is deprecated since Symfony 3.2 and won't be supported anymore in Symfony 4.0

However if you use PhpUnitBridge with weak_vendors mode introduced in #21539, then this deprecation notice will be silenced.

I'm not sure if that's the expected behaviour, my understanding of weak_vendors was that third-party deprecations, as a third-party bundle using a deprecated feature, would be silenced, not any deprecation thrown by Symfony itself triggered or not by your code.

Steps to reproduce:

• clone https://github.com/theofidry/phpunitbridge-demo2
• composer install
• ./tests.sh

Inside tests.sh we can see that with weak_vendors, all deprecation notices are caught whereas without it, the deprecation notice for requesting private services is thrown (and is triggered by the user code).

/cc @greg0ire