We were simply using this to get a list of language codes. Turns out
Python provides a way to do this already via the 'locale' module, which
provides all of the locales we care about [1]. Use this.
[1] https://github.com/python/cpython/blob/3.5/Lib/locale.py
Change-Id: Id6dce33fdbe3fc537dfe28d5cc604985b3347405
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>