service_unix - error text is not informative

[sg3des]

Hello. If the command, example start, failed, in output writed only error code, example: "systemctl" failed: exit status 5 - it is not informative.
On my opinion, in function: service_unix:55 func run, if you want to process stderr buffer, better to use bytes.Buffer instead of StderrPipe:

var buf bytes.Buffer
cmd.Stderr = &buf
[...]
if command == "launchctl" {
	if buf.Len() > 0 {
		return fmt.Errorf("%q failed with stderr: %s", command, buf.String())
	}
}
if err := cmd.Wait(); err != nil {
	return fmt.Errorf("%q failed: %s", command, buf.String())
}

In the error will write a valid output from the service, example for systemctl: Failed to start name.service: Unit name.service not found.