Translate available preferred languages in user account settings

The listed languages in the "preferred languages" input dropdown should
be translated in the user language.

common/djangoapps/lang_pref/api.py

@@ -4,6 +4,7 @@
 from collections import namedtuple
 
 from django.conf import settings
+from django.utils.translation import ugettext as _
 from dark_lang.models import DarkLangConfig
 
 
@@ -45,3 +46,16 @@ def released_languages():
     ]
 
     return released_languages
+
+
+def all_languages():
+    """Retrieve the list of all languages, translated and sorted.
+
+    Returns:
+        list of (language code (str), language name (str)): the language names
+        are translated in the current activated language and the results sorted
+        alphabetically.
+
+    """
+    languages = [(lang[0], _(lang[1])) for lang in settings.ALL_LANGUAGES]  # pylint: disable=translation-of-non-string
+    return sorted(languages, key=lambda lang: lang[1])

common/djangoapps/lang_pref/tests/test_api.py

@@ -2,6 +2,8 @@
 """ Tests for the language API. """
 
 from django.test import TestCase
+from django.test.utils import override_settings
+from django.utils import translation
 from lang_pref import api as language_api
 
 
@@ -10,3 +12,15 @@ class LanguageApiTest(TestCase):
     def test_released_languages(self):
         released_languages = language_api.released_languages()
         self.assertGreaterEqual(len(released_languages), 1)
+
+    @override_settings(ALL_LANGUAGES=[[u"cs", u"Czech"], [u"nl", u"Dutch"]])
+    def test_all_languages(self):
+        with translation.override('fr'):
+            all_languages = language_api.all_languages()
+
+        self.assertEqual(2, len(all_languages))
+        self.assertLess(all_languages[0][1], all_languages[1][1])
+        self.assertEqual("nl", all_languages[0][0])
+        self.assertEqual("cs", all_languages[1][0])
+        self.assertEqual(u"Hollandais", all_languages[0][1])
+        self.assertEqual(u"Tchèque", all_languages[1][1])