Make go vet ./... happy

Signed-off-by: David Gageot <david@gageot.net>

commands/commands_test.go

@@ -205,7 +205,9 @@ func TestReturnExitCode1onError(t *testing.T) {
 
 func TestReturnExitCode3onErrorDuringPreCreate(t *testing.T) {
 	command := func(commandLine CommandLine, api libmachine.API) error {
-		return mcnerror.ErrDuringPreCreate{errors.New("foo is not bar")}
+		return mcnerror.ErrDuringPreCreate{
+			Cause: errors.New("foo is not bar"),
+		}
 	}
 
 	exitCode := checkErrorCodeForCommand(command)

libmachine/host/host_test.go

@@ -69,7 +69,7 @@ func NewNetstatProvisioner() provision.Provisioner {
 
 func TestStart(t *testing.T) {
 	provision.SetDetector(&provision.FakeDetector{
-		NewNetstatProvisioner(),
+		Provisioner: NewNetstatProvisioner(),
 	})
 
 	host := &Host{

libmachine/libmachine.go

@@ -123,7 +123,9 @@ func (api *Client) Create(h *host.Host) error {
 	log.Info("Running pre-create checks...")
 
 	if err := h.Driver.PreCreateCheck(); err != nil {
-		return mcnerror.ErrDuringPreCreate{err}
+		return mcnerror.ErrDuringPreCreate{
+			Cause: err,
+		}
 	}
 
 	if err := api.Save(h); err != nil {