Fix error handling for parsed output (#23)

* Fix error handling for parsed output

pkg/mc/mc.go

@@ -240,15 +240,17 @@ func do(done chan bool, context string, namespace string, output map[string]json
 	stdout, err := kubectl(cmd)
 	if err != nil {
 		stdout = []byte(err.Error())
-	}
-	mutex.Lock()
+		logger.Debug("kubectl error", zap.Error(err))
+	} else {
+		mutex.Lock()
 
-	cns := context
-	if namespace != "" {
-		cns += ": " + namespace
+		cns := context
+		if namespace != "" {
+			cns += ": " + namespace
+		}
+		output[cns] = stdout
+		mutex.Unlock()
 	}
-	output[cns] = stdout
-	mutex.Unlock()
 	if writeToStdout {
 		fmt.Fprint(out, formatContext(context, namespace, stdout))
 	}
@@ -259,7 +261,11 @@ func do(done chan bool, context string, namespace string, output map[string]json
 func kubectl(cmd Cmd) ([]byte, error) {
 	out, err := cmd.Output()
 	if err != nil {
-		return nil, fmt.Errorf(strings.Replace(strings.Replace(string(out), "error: ", "", -1), "Error: ", "", -1))
+		errString := err.Error()
+		if err, ok := err.(*exec.ExitError); ok {
+			errString = string(err.Stderr)
+		}
+		return nil, fmt.Errorf(strings.Replace(strings.Replace(errString, "error: ", "", -1), "Error: ", "", -1))
 	}
 	return out, nil
 }

pkg/mc/mc_test.go

@@ -3,8 +3,8 @@ package mc
 import (
 	"bytes"
 	"encoding/json"
-	"errors"
 	"io/ioutil"
+	"os/exec"
 	"sync"
 	"testing"
 
@@ -188,8 +188,8 @@ func TestKubectl(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, kubectlReturn, got)
 
-	m.EXPECT().Output().Return([]byte(`Error: unknown shorthand flag: 'a' in -abc
-See 'kubectl get --help' for usage.`), errors.New(""))
+	m.EXPECT().Output().Return(nil, &exec.ExitError{Stderr: []byte(`Error: unknown shorthand flag: 'a' in -abc
+See 'kubectl get --help' for usage.`)})
 
 	got, err = kubectl(m)
 	assert.Nil(t, got)