Default to fr_FR.UTF8 locale if accept-language is broken

webapp.py

@@ -42,7 +42,10 @@ def set_locale():
     accept_language = request.get_header("Accept-Language", "fr-FR")
     first_lang = accept_language.split(";")[0].split(",")[0]
     lang = first_lang.translate(str.maketrans("-", "_")) + ".UTF-8"
-    locale.setlocale(locale.LC_ALL, lang)
+    try:
+        locale.setlocale(locale.LC_ALL, lang)
+    except locale.Error:
+        locale.setlocale(locale.LC_ALL, "fr_FR.UTF-8")
 
 
 @hook("before_request")