Error when `django.middleware.locale.LocaleMiddleware` or `donottrack.middleware.DoNotTrackMiddleware` come after `django.middleware.cache.UpdateCacheMiddleware`.

gistfile1.pytb

Environment:


Request Method: GET
Request URL: http://localhost:8000/

Django Version: 1.5
Python Version: 3.3.0
Installed Applications:
('foo',)
Installed Middleware:
('django.middleware.cache.UpdateCacheMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.locale.LocaleMiddleware',
 'django.middleware.cache.FetchFromCacheMiddleware')


Traceback:
File "/Users/benspaulding/.virtualenvs/foo/lib/python3.3/site-packages/django/core/handlers/base.py" in get_response
  187.                 response = middleware_method(request, response)
File "/Users/benspaulding/.virtualenvs/foo/lib/python3.3/site-packages/django/middleware/cache.py" in process_response
  109.             cache_key = learn_cache_key(request, response, timeout, self.key_prefix, cache=self.cache)
File "/Users/benspaulding/.virtualenvs/foo/lib/python3.3/site-packages/django/utils/cache.py" in learn_cache_key
  242.         return _generate_cache_key(request, request.method, headerlist, key_prefix)
File "/Users/benspaulding/.virtualenvs/foo/lib/python3.3/site-packages/django/utils/cache.py" in _generate_cache_key
  184.             ctx.update(value)

Exception Type: TypeError at /
Exception Value: Unicode-objects must be encoded before hashing