Normalize language to include country code

Since changeset 66058a05f1, the language can be two code only so we need to
normalize it as the DPD API always requires the country code.

issue5976
review27761002

carrier.py

@@ -1,5 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+import locale
+
 from zeep.exceptions import Fault
 
 from trytond.model import ModelSQL, ModelView, MatchMixin, fields
@@ -40,6 +42,7 @@ class CredentialDPD(ModelSQL, ModelView, MatchMixin):
         auth_client = get_client(self.server, LOGIN_SERVICE)
         lang = (self.company.party.lang.code
             if self.company.party.lang else 'en')
+        lang = locale.normalize(lang)[:5]
         try:
             result = auth_client.service.getAuth(
                 delisId=self.user_id, password=self.password,

stock.py

@@ -1,6 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 
+import locale
 from io import BytesIO
 from lxml import etree
 from zeep.exceptions import Fault
@@ -102,6 +103,7 @@ class CreateDPDShipping(Wizard):
         while count < 2:
             lang = (credential.company.party.lang.code
                 if credential.company.party.lang else 'en')
+            lang = locale.normalize(lang)[:5]
             authentication = {
                 'delisId': credential.user_id,
                 'authToken': credential.token,