Comment 3 for bug 1179526

It seems en-us (or en_US) cannot be used as a language name in Django. The available languages in Django are defined in LANG_INFO in django.conf.locale.__init__.py.

Regarding Transifex side, the source language of each project cannot be changed after the project is created (through Web UI and API). Thus I am afraid we need to delete and recreate the Horizon project.

If OpenStack has an official channel to talk with Transifex support team, it is the best way.

The best way is to change the source language in Horizon from en_US to en, but it may take some time.
Before finishing the fix, we can avoid the case where 'en' lang in git repo is updated by mistake
by adding the following language_map to .tx/config temporarily.
---
lang_map = en_US: en, en: _dummy
---
(http://help.transifex.com/features/client/index.html#customizing-the-language-mappings)