LocaleMiddleware should not set Content-Language header if already present
|Reported by:||Joost Cassee||Owned by:||nobody|
|Cc:||Triage Stage:||Ready for checkin|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
The user may have added the Content-Language header to the Response objects explicitely. In that case LocaleMiddleware should not overwrite it. Attached patch fixes this.