Default to English on unsupported system language Fix #976

- Add check for supported language to system locale detection
- Fall-back to English when not a supported locale

hscommon/trans.py

@@ -150,7 +150,9 @@ def install_gettext_trans_under_qt(base_folder, lang=None):
     if not lang:
         lang = str(QLocale.system().name())[:2]
     localename = get_locale_name(lang)
-    if localename is not None:
+    if localename is None:
+        lang = "en"
+        localename = get_locale_name(lang)
     try:
         locale.setlocale(locale.LC_ALL, localename)
     except locale.Error: