Provide fallback for Django 1.6

This variable started to exist in Django 1.7.
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/accounts/models.py

@@ -33,7 +33,13 @@ from django.db.models.signals import post_syncdb
 from django.utils import translation as django_translation
 from django.template.loader import render_to_string
 from django.core.mail import EmailMultiAlternatives
-from django.utils.translation import LANGUAGE_SESSION_KEY
+try:
+    # Not supported in Django 1.6
+    # pylint: disable=E0611
+    from django.utils.translation import LANGUAGE_SESSION_KEY
+except ImportError:
+    # Fallback for Django 1.6
+    LANGUAGE_SESSION_KEY = 'django_language'
 
 from social.apps.django_app.default.models import UserSocialAuth
 

weblate/accounts/views.py

@@ -36,7 +36,9 @@ try:
     # pylint: disable=E0611
     from django.contrib.auth import update_session_auth_hash
 except ImportError:
+    # Fallback for Django 1.6
     update_session_auth_hash = None
+
 from urllib import urlencode
 
 from weblate.accounts.forms import (