This reverts commit a88092630014c53c9e6fe4ee9265f8443eea96bd.
The reverted implementation depends on LOCALE_PATHS but this assumption
turns out not correct. Django searches messages catalogs LOCALE_PATHS
and locale directory in individual INSTALLED_APPS, but the usage of
LOCALE_PATHS varies on deployers and we cannot assume the default value
of LOCALE_PATSH.
In addition, the logic of auto-generating the language list cannot
handle locale name alias ('fallback' in the Django code).
Django 1.9 or later perfers to zh-hant and zh-hans, and zh-cn and
zh-tw are now defined as fallback.
We can explore a better approach for auto-generation of the language
list, but we do not have more reliable way so far. Cconsidering the
timing of Pike release, the safest approach looks like to revert
the original patch back to the manula maintenance of the lang list.
Languages with over 50% progress (based on the number of translated
messages as total) are listed in settings.LANGUAGES.
(http://paste.openstack.org/show/618254/)
Closes-Bug: #1710131
Change-Id: I5133d6317aba6107fc37bd5f30388c130b1fdaac
00f74fc06c