Issue title: Error building mlo language pack
 Issue body: _Reported by Akmal Khushvakov (uzbadmin)_

I am trying build new Uzbek language pack. But it doesn’t work. It says: 

```
Error: Requested content 'mozilla.locamotion.org/uz/firefox/?ext_actions=Build+language+pack' cannot be resolved.
```

Can you make for me this work?

 Comments: 
 Comment 0: This is building locally i.e. if you are logged into mlo.  But still not working with a Pootle driven build

 Comment 1: MLO removed the option to build any language packs, closing.
{'source': 'GithubIssues', 'repo_name_with_owner': 'translate/pootle', 'issue_id': 38979170, 'repo_stars': 1440.0}