use python fallback to avoid error on old mongo version without roles

database/misc/mongodb_user.py

@@ -265,7 +265,7 @@ def main():
         uinfo = user_find(client, user, db_name)
         if update_password != 'always' and uinfo:
             password = None
-            if 'roles' in uinfo and list(map((lambda x: x['role']), uinfo['roles'])) == roles:
+            if list(map((lambda x: x['role']), uinfo.get('roles', []))) == roles:
                 module.exit_json(changed=False, user=user)
 
         try: