'Given an an activation key, look up and activate the user
account corresponding to that key (if possible).
After successful activation, the signal
``registration.signals.user_activated`` will be sent, with the
newly activated ``User`` as the keyword argument ``user`` and
the class of this backend as the sender.'

def activate(self, *args, **kwargs):

    activation_key = kwargs.get('activation_key', '')
    site = get_current_site(self.request)
    activated_user = self.registration_profile.objects.activate_user(activation_key, site)
    if activated_user:
        signals.user_activated.send(sender=self.__class__, user=activated_user, request=self.request)
    return activated_user
