change error format

cmd/ls.go

@@ -25,7 +25,7 @@ func LsCmd(args CmdArgs) int {
 	selector := args.Flags.String("selector")
 	lights, err := c.ListLights(selector)
 	if err != nil {
-		fmt.Println(err)
+		fmt.Printf("fatal: %s\n", err)
 		return 1
 	}
 	PrintLights(lights)

cmd/lume/main.go

@@ -47,7 +47,7 @@ func main() {
 
 	cmd, ok := lumecmd.GetCommand(command)
 	if !ok {
-		fmt.Println("ERROR")
+		fmt.Printf("lume: '%s' is not lume command. See 'lume' --help.'\n", command)
 		os.Exit(1)
 	}
 	fs := cmd.Flags

cmd/toggle.go

@@ -24,7 +24,7 @@ func ToggleCmd(args CmdArgs) int {
 	selector := args.Flags.String("selector")
 	r, err := c.Toggle(selector, duration)
 	if err != nil {
-		fmt.Println(err)
+		fmt.Printf("fatal: %s\n", err)
 		return 1
 	}
 	PrintResults(r.Results)