[1.8.x] Fixed #26046 -- Fixed a crash with translations and Django-unknown language code

Thanks Jens Lundstrom for the report and Tim Graham for the review.
Backport of 632a9f21bc from master.

django/utils/translation/trans_real.py

@@ -121,6 +121,9 @@ class DjangoTranslation(gettext_module.GNUTranslations):
             # default lang should have at least one translation file available.
             raise IOError("No translation files found for default language %s." % settings.LANGUAGE_CODE)
         self._add_fallback()
+        if self._catalog is None:
+            # No catalogs found for this language, set an empty catalog.
+            self._catalog = {}
 
     def __repr__(self):
         return "<DjangoTranslation lang:%s>" % self.__language

docs/releases/1.8.9.txt

@@ -11,3 +11,6 @@ Bugfixes
 
 * Fixed a regression that caused the "user-tools" items to display on the
   admin's logout page (:ticket:`26035`).
+
+* Fixed a crash in the translations system when the current language has no
+  translations (:ticket:`26046`).

tests/i18n/tests.py

@@ -1273,6 +1273,10 @@ class TestLanguageInfo(TestCase):
 
     def test_unknown_language_code(self):
         six.assertRaisesRegex(self, KeyError, r"Unknown language code xx\.", get_language_info, 'xx')
+        with translation.override('xx'):
+            # A language with no translation catalogs should fallback to the
+            # untranslated string.
+            self.assertEqual(ugettext("Title"), "Title")
 
     def test_unknown_only_country_code(self):
         li = get_language_info('de-xx')