misc: get language from default locale if none specified (#7343)

wcs/qommon/publisher.py

@@ -25,6 +25,7 @@ import imp
 import os
 import fcntl
 import json
+import locale
 import random
 import socket
 import sys
@@ -600,6 +601,10 @@ class QommonPublisher(Publisher):
                 for l in accepted_languages:
                     if l in self.translations.keys():
                         return l
+        elif lang is None:
+            default_locale = locale.getdefaultlocale()
+            if default_locale and default_locale[0]:
+                lang = default_locale[0].split('_')[0]
         return lang
 
     def get_admin_module(cls):