Figures out the full host name for the given domain part.  The
        domain part is a subdomain in case host matching is disabled or
        a full host name.

def get_host(self, domain_part):
        """Figures out the full host name for the given domain part.  The
        domain part is a subdomain in case host matching is disabled or
        a full host name.
        """
        if self.map.host_matching:
            if domain_part is None:
                return self.server_name
            return to_unicode(domain_part, "ascii")
        subdomain = domain_part
        if subdomain is None:
            subdomain = self.subdomain
        else:
            subdomain = to_unicode(subdomain, "ascii")
        return (subdomain + u"." if subdomain else u"") + self.server_name