code: function restifyErrorHandler(client, config, err, em) {
    var svc = config.getServiceContext();
    em.setServiceContext(svc.service, svc.version);
  
    errorHandlerRouter(err, em);
  
    client.sendError(em);
  }
docs: The restifyErrorHandler is responsible for taking the captured error, setting
  the serviceContext property on the corresponding ErrorMessage instance,
  routing the captured error to the right handler so that it can be correctly
  marshaled into the ErrorMessage instance and then attempting to send it to
  the Stackdriver API via the given API client instance.
  @function restifyErrorHandler
  @param {AuthClient} client - the API client
  @param {NormalizedConfigurationVariables} config - the application
  configuration
  @param {Any} err - the error being handled
  @param {ErrorMessage} - the error message instance container
  @returns {Undefined} - does not return anything