1) The product_details_json directory must exist before ./manage.py
syncdb is run (otherwise it fails)
2) running ./manage.py update_product_details requires a configured DB
3) the main page currently fails with an exception if you don't run
update_product_details, so it's not an optional step.
SITE_URL is described at https://github.com/mozilla/django-browserid/blob/master/docs/setup.rst
PROTOCOL, DOMAIN, and PORT are not strictly required for browserid to
work, but I guess it wouldn't hurt to override the default values in
SESSION_COOKIE_SECURE is required, since otherwise the session cookie
gets lost because the development server is not https://.