code: function HKP(keyServerBaseUrl) {
    this._baseUrl = keyServerBaseUrl || config.keyserver;
    this._fetch = typeof window !== 'undefined' ? window.fetch : require('node-fetch');
  }
docs: Initialize the HKP client and configure it with the key server url and fetch function.
  @constructor
  @param {String}    keyServerBaseUrl  (optional) The HKP key server base url including
  the protocol to use, e.g. 'https://pgp.mit.edu'; defaults to
  openpgp.config.keyserver (https://keyserver.ubuntu.com)