def get_default_billing_address(self):
        if not self.request.user.is_authenticated():
            return None
        try:
            return self.request.user.addresses.get(is_default_for_billing=True)
        except UserAddress.DoesNotExist:
            return None
This has to logout the user again.  This method must not fail.
dataset/ETHPy150Open django-oscar/django-oscar/src/oscar/apps/checkout/views.py/PaymentDetailsView.get_default_billing_address--crossover with--dataset/ETHPy150Open mitsuhiko/solace/solace/auth.py/AuthSystemBase.logout