How to use the josepy.util.ComparableX509 function in josepy

def request_certificate(logger, acme_client, elb_name, authorizations, csr):
    logger.emit("updating-elb.request-cert", elb_name=elb_name)
    cert_response, _ = acme_client.poll_and_request_issuance(
        josepy.util.ComparableX509(
            OpenSSL.crypto.load_certificate_request(
                OpenSSL.crypto.FILETYPE_ASN1,
                csr.public_bytes(serialization.Encoding.DER),
            )
        ),
        authzrs=[authz_record.authz for authz_record in authorizations],
    )
    pem_certificate = OpenSSL.crypto.dump_certificate(
        OpenSSL.crypto.FILETYPE_PEM, cert_response.body
    )
    pem_certificate_chain = b"\n".join(
        OpenSSL.crypto.dump_certificate(OpenSSL.crypto.FILETYPE_PEM, cert)
        for cert in acme_client.fetch_chain(cert_response)
    )
    return pem_certificate, pem_certificate_chain

def revoke(ctx, reason, cert_paths):
    '''
    Revoke existing certificates.
    '''
    for cert_path in cert_paths:
        with open(cert_path, 'rb') as certfile:
            crt = crypto.load_certificate(crypto.FILETYPE_PEM, certfile.read())
            try:
                ctx.obj.acme.revoke(ComparableX509(crt), REVOCATION_REASONS[reason])
            except messages.Error as e:
                logger.error(e)

def _generate_csr(key, key_digest, domains):
    csr = crypto.X509Req()
    csr.set_version(2)
    csr.set_pubkey(key)

    sans = ', '.join('DNS:{}'.format(d) for d in domains)
    exts = [crypto.X509Extension(b'subjectAltName', False, b(sans))]
    csr.add_extensions(exts)

    csr.sign(key, str(key_digest))

    return ComparableX509(csr)

regr = acme.register()
logging.info('Auto-accepting TOS: %s', regr.terms_of_service)
acme.agree_to_tos(regr)
logging.debug(regr)

authzr = acme.request_challenges(
    identifier=messages.Identifier(typ=messages.IDENTIFIER_FQDN, value=DOMAIN))
logging.debug(authzr)

authzr, authzr_response = acme.poll(authzr)

csr = OpenSSL.crypto.load_certificate_request(
    OpenSSL.crypto.FILETYPE_ASN1, pkg_resources.resource_string(
        'acme', os.path.join('testdata', 'csr.der')))
try:
    acme.request_issuance(jose.util.ComparableX509(csr), (authzr,))
except messages.Error as error:
    print ("This script is doomed to fail as no authorization "
           "challenges are ever solved. Error from server: {0}".format(error))