'Check for new cert.
:param certr: Certificate Resource
:type certr: `.CertificateResource`
:returns: Updated Certificate Resource.
:rtype: `.CertificateResource`'

def check_cert(self, certr):

    (response, cert) = self._get_cert(certr.uri)
    if ('Location' not in response.headers):
        raise errors.ClientError('Location    header    missing')
    if (response.headers['Location'] != certr.uri):
        raise errors.UnexpectedUpdate(response.text)
    return certr.update(body=cert)
