@classmethod
def _sync_blank_domain(cls, site):
    """Delete associated Alias object for ``site``, if domain is blank."""
    if site.domain:
        raise ValueError('%r has a domain' % site)
    try:
        alias = cls.objects.get(site=site)
    except cls.DoesNotExist:
        pass
    else:
        if not alias.is_canonical:
            raise cls.MultipleObjectsReturned('Other %s still exist for %r' %
                (cls._meta.verbose_name_plural.capitalize(), site))
        alias.delete()
