Validate username format in what seem to be WIP API?

dal/views.py

@@ -511,6 +511,10 @@ class UserCreateAPI(APIView):
 
         if username == "" or not username:
             return Response('Please supply a username.', 400)
+
+        if not is_username_valid(username):
+            return Response('Username is not valid.', 400)
+
         try:
             validate_email(email)
         except ValidationError: