I use django-lockdown for exactly this purpose. It allows you to add a simple password over the whole of a dev site, without having to add in any extra auth bits on your views that aren't used outside of a dev environment. It also means you can login as admin, or regular users to test whatever your site does
https://github.com/Dunedan/django-lockdown
I use Heroku and Lockdown with this bit of code in my settings.py file
USE_LOCKDOWN = os.environ.get('USE_LOCKDOWN', 'False') == 'True'
if USE_LOCKDOWN:
INSTALLED_APPS += ('lockdown',)
MIDDLEWARE_CLASSES += ('lockdown.middleware.LockdownMiddleware',)
LOCKDOWN_PASSWORDS = (os.environ.get('LOCKDOWN_PASSWORD', 'False'),)
LOCKDOWN_URL_EXCEPTIONS = (r'^/some/url/not/locked/down/$',)
Then obviously set a config var of USE_LOCKDOWN as True on my dev site, and False on my production site so no need to change the code for either.