It's nice to be able to test your 404.html and 500.html templates in your development environment before you push to production.

You could use direct_to_template, but it would be better to use the default Django views that the errors actually use. These are "django.views.defaults.server_error" and "django.views.defaults.page_not_found". All you need to do is to add these to your urlpatterns in a conditonal statement for local development. *** note the += ***

# urls.py

urlpatterns = patterns('',
    ...
)

if settings.LOCAL_DEV:
    urlpatterns += patterns('',
        (r'^404/$', 'django.views.defaults.page_not_found'),
        (r'^500/$', 'django.views.defaults.server_error'),
        (r'^media/(?P.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT} ),
    )

If you're using Django-CMS this is not going to work because the cms page middleware will call the 404 error before it gets to the LOCAL_DEV urls. This is easily fixed by moving the cms url include to after the LOCAL_DEV urls.

urlpatterns += patterns('',
    url(r'^', include('cms.urls')), # put this near the end
)