from registration.backends.default import DefaultBackend


class RedirectBackend(DefaultBackend):

    def register(self, request, **kwargs):
        request.session['redirect'] = request.GET.get('next', None)
super(RedirectBackend, self).register(request, **kwargs)

def post_activation_redirect(self, request, user):
    return request.session['redirect'], (), {}
Getting `django-registration` to send you to the page you were originally trying to visit