helper/communicator: ssh settings aren't required if type is none

helper/communicator/config.go

@@ -35,8 +35,10 @@ func (c *Config) Prepare(ctx *interpolate.Context) []error {
 
 	// Validation
 	var errs []error
-	if c.SSHUsername == "" {
-		errs = append(errs, errors.New("An ssh_username must be specified"))
+	if c.Type == "ssh" {
+		if c.SSHUsername == "" {
+			errs = append(errs, errors.New("An ssh_username must be specified"))
+		}
 	}
 
 	return errs

helper/communicator/config_test.go

@@ -23,6 +23,13 @@ func TestConfigType(t *testing.T) {
 	}
 }
 
+func TestConfig_none(t *testing.T) {
+	c := &Config{Type: "none"}
+	if err := c.Prepare(testContext(t)); len(err) > 0 {
+		t.Fatalf("bad: %#v", err)
+	}
+}
+
 func testContext(t *testing.T) *interpolate.Context {
 	return nil
 }