code: function (error, callback, verbosity) {
      if (callback) {
        callback(error)
      } else {
        module.exports.logError(error, {verbosity: verbosity})
      }
    }
docs: Invokes a callback with the supplied `Error`.
  @param {Error} error - The error.
  @param {Function} callback - Callback to invoke. If null, the `Error`
  is written to a log.
  @param {Number} [verbosity] - Level of verbosity at which to log the
  error message if the callback is not invoked.