def get_cas_client(self, request, provider, renew=False):
        """
            return a CAS client object matching provider

            :param django.http.HttpRequest request: The current request object
            :param cas_server.models.FederatedIendityProvider provider: the user identity provider
            :return: The user CAS client object
            :rtype: :class:`federate.CASFederateValidateUser
                <cas_server.federate.CASFederateValidateUser>`
        """
        # compute the current url, ignoring ticket dans provider GET parameters
        service_url = utils.get_current_url(request, {"ticket", "provider"})
        self.service_url = service_url
        return CASFederateValidateUser(provider, service_url, renew=renew)