Document if language identifiers in Local are case sensitive

[techtonik]

I could not find if language name supplied to Locale() constructor is case sensitive. There is no format on language identifiers neither at http://babel.pocoo.org/docs/locale/ nor at http://babel.pocoo.org/docs/api/core/#babel.core.Locale

Got this problem at gratipay/gratipay.com#2890

[jeremydw]

After doing some research on this myself, it looks like it's case-sensitive for case-sensitive filesystems and not case-sensitive for filesystems that aren't. You can verify by inspecting how Babel determines whether a locale exists or not, and how it loads the locale data files:

https://github.com/mitsuhiko/babel/blob/master/babel/localedata.py#L35

[jeremydw]

By the way, I think CLDR's spec says that locale identifiers should NOT be case sensitive (http://cldr.unicode.org/core-spec – search for "case-insensitive" – "All identifier field values are case-insensitive.") so if that's indeed true I think it'd be nice if Babel could normalize this somehow to support case-insensitivity independent of the filesystem.

[akx]

#309 will fix this in the sense that it will become impossible to create a en_us locale (should be en_US).

[akx]

#814 is related to this case (in)sensitivity.