code: func Exec(cmd string, args ...string) (string, error) {
  	if testMode {
  		return testModeExec(cmd, args...)
  	}
  
  	glog.V(5).Infof("[cmd] %s %s", cmd, strings.Join(args, " "))
  	out, err := osexec.Command(cmd, args...).CombinedOutput()
  	if err != nil {
  		err = fmt.Errorf("%s failed: '%s %s': %v", cmd, cmd, strings.Join(args, " "), err)
  	} else if glog.V(5) {
  		lines := strings.Split(string(out), "\n")
  		for i, line := range lines {
  			if i < len(lines)-1 || len(line) > 0 {
  				glog.V(5).Infof("[cmd]   => %s", line)
  			}
  		}
  	}
  	return string(out), err
  }
docs: // Exec executes a command with the given arguments and returns either the
  // combined stdout+stdin, or an error.