rc: return error from remote on failure

cmd/rc/rc.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"os"
 	"strings"
@@ -39,7 +40,7 @@ Arguments should be passed in as parameter=value.
 
 The result will be returned as a JSON object by default.
 
-Use "rclone rc list" to see a list of all possible commands.`,
+Use "rclone rc" to see a list of all possible commands.`,
 	Run: func(command *cobra.Command, args []string) {
 		cmd.CheckArgs(0, 1E9, command, args)
 		cmd.Run(false, false, command, func() error {
@@ -80,6 +81,19 @@ func doCall(path string, in rc.Params) (out rc.Params, err error) {
 	}
 	defer fs.CheckClose(resp.Body, &err)
 
+	if resp.StatusCode != http.StatusOK {
+		var body []byte
+		body, err = ioutil.ReadAll(resp.Body)
+		var bodyString string
+		if err == nil {
+			bodyString = string(body)
+		} else {
+			bodyString = err.Error()
+		}
+		bodyString = strings.TrimSpace(bodyString)
+		return nil, errors.Errorf("Failed to read rc response: %s: %s", resp.Status, bodyString)
+	}
+
 	// Parse output
 	out = make(rc.Params)
 	err = json.NewDecoder(resp.Body).Decode(&out)