code: public X509CRL getRevocationList(final X509Certificate identity,
              final PrivateKey key, final X500Principal issuer,
              final BigInteger serial) throws ClientException,
              OperationFailureException {
          return getRevocationList(identity, key, issuer, serial, null);
      }
docs: Returns the certificate revocation list a given issuer and serial number.
  <p>
  This method requests a CRL for a certificate as identified by the issuer
  name and the certificate serial number.
  
  @param identity
  the identity of the client.
  @param key
  the private key to sign the SCEP request.
  @param issuer
  the name of the certificate issuer.
  @param serial
  the serial number of the certificate.
  @return the CRL corresponding to the issuer and serial.
  @throws ClientException
  if any client errors occurs.
  @throws OperationFailureException
  if the request fails.