fixed translator locale when dealing with sub-requests

| Q             | A
| ------------- | ---
| Bug fix?      | yes, kinda
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

This fixes the (edge) case where the locale of a sub-requests is different from the locale of the master request. The listener synchronizes the translator locale with the one from the request.


The \InvalidArgumentException is not catched as it was done in the Translator. Thus users can throw internal errors by requesting an invalid locale.