Comment 11 for bug 590108

Despite the general subject, I'm going to restrict this bug to the case of those languages where the choice of location may get you a different localisation (due to different dialect, writing system, etc.): of the languages we support for installation, that's Portuguese and Chinese. There is also a problem of what should happen if (say) you select English but then say you live in Switzerland, or select Chinese but say you live in France; that is a much harder problem and I would appreciate not having the scope of this bug widened to include that. All the people who've commented on this bug so far seem to be concerned with the case of zh_CN vs. zh_TW.

To fix this, we need to change both localechooser and ubiquity. The approach I'll take is modelled on that of language-selector; in cases where they mismatch, LANG should primarily reflect the location (so that numeric, monetary, etc. locale categories are correct) while LANGUAGE, LC_MESSAGES, LC_CTYPE, and LC_COLLATE should primarily reflect the language.