docs: function makeExpressHandler(client, config) {
    /**
     * The Express Error Handler function is an interface for the error handler
     * stack into the Express architecture.
     * @function expressErrorHandler
     * @param {Any} err - a error of some type propagated by the express plugin
     *  stack
     * @param {Object} req - an Express request object
     * @param {Object} res - an Express response object
     * @param {Function} next - an Express continuation callback
     * @returns {ErrorMessage} - Returns the ErrorMessage instance
     */
    function expressErrorHandler(err, req, res, next) {
      var ctxService = '';
      var ctxVersion = '';
      
      if (isObject(config)) {
        ctxService = config.getServiceContext().service;
        ctxVersion = config.getServiceContext().version;
      }
  
      var em = new ErrorMessage()
                   .consumeRequestInformation(
                       expressRequestInformationExtractor(req, res))
                   .setServiceContext(ctxService, ctxVersion);
  
      errorHandlerRouter(err, em);
  
      if (isObject(client) && isFunction(client.sendError)) {
        client.sendError(em);
      }
  
      if (isFunction(next)) {
        next(err);
      }
  
      return em;
    }
  
    return expressErrorHandler;
  }