code: function checkRevocationKey(signature, keyId) {
    if (signature.revocationKeyClass !== null &&
        signature.issuerKeyId.equals(keyId)) {
      throw new Error('This key is intended to be revoked with an authorized key, which OpenPGP.js does not support.');
    }
  }
docs: Check if signature has revocation key sub packet (not supported by OpenPGP.js)
  and throw error if found
  @param {module:packet.Signature} signature The certificate or signature to check
  @param {type/keyid} keyId Check only certificates or signatures from a certain issuer key ID