Modify the locale middleware in python to not look at the HTTP_ACCEPT_LANGUAGE header (and just use the language specified in the settings or the user's preferences)

middleware.py

import os
import sys
import re

from django.utils import translation
from django.middleware.locale import LocaleMiddleware

class LocaleNoHTTPAcceptMiddleware(LocaleMiddleware):
    def process_request(self, request):
        request.LANGUAGE_CODE = translation.get_language()

# Now just remember to do the following in your settings:
# MIDDLEWARE_CLASSES = [
#     ...
#    'django.middleware.locale.LocaleMiddleware',
#    '<appname>.middleware.LocaleNoHTTPAcceptMiddleware',
#     ...
# ]