code: function publishRobotsTxt () {
      var path = 'robots.txt';
      return fs
          .statAsync(path)
          .then(function (pStat) {
              if (!pStat.isFile()) {
                  // go to our default course of action, that is create robots.txt file
                  throw new Error ();
              }
          })
          .catch(Error, function () {
              return fs
                  .openAsync(path, 'w')
                  .then(function () {
                      return fs.writeFileAsync(path, 'User-agent: *\nSitemap: ' + config.siteUrl + '/sitemap.xml');
                  })
                  .catch(function (pErr) {
                      log.error(pErr);
                  });
          });
  }
docs: Creates a default robots.txt file if it does not exist
  @returns {*}