code: function execFile(cmd, args, opts) {
      return new Promise(function(resolve, reject) {
          childProcess.execFile(cmd, args, opts, function(err, stdout, stderr) {
              if (err) {
                  console.error("Error executing " + cmd + " " + args.join(" "));
                  console.error(stdout + stderr);
                  err.stdout = stdout;
                  err.stderr = stderr;
                  reject(err);
              } else {
                  resolve(stdout);
              }
          });
      });
  }
docs: Execute a given command, and return a promise to its output.