Adding apiVersion guidance to the linting

Signed-off-by: Matt Farina <matt@mattfarina.com>

pkg/lint/lint_test.go

@@ -63,7 +63,7 @@ func TestBadChart(t *testing.T) {
 				e3 = true
 			}
 
-			if strings.Contains(msg.Err.Error(), "apiVersion is required") {
+			if strings.Contains(msg.Err.Error(), "apiVersion is required. The value must be either \"v1\" or \"v2\"") {
 				e4 = true
 			}
 		}

pkg/lint/rules/chartfile.go

@@ -89,7 +89,7 @@ func validateChartNameDirMatch(chartDir string, cf *chart.Metadata) error {
 
 func validateChartAPIVersion(cf *chart.Metadata) error {
 	if cf.APIVersion == "" {
-		return errors.New("apiVersion is required")
+		return errors.New("apiVersion is required. The value must be either \"v1\" or \"v2\"")
 	}
 
 	if cf.APIVersion != "v1" && cf.APIVersion != "v2" {

pkg/lint/rules/chartfile_test.go

@@ -221,7 +221,7 @@ func TestChartfile(t *testing.T) {
 		t.Errorf("Unexpected message 1: %s", msgs[1].Err)
 	}
 
-	if !strings.Contains(msgs[2].Err.Error(), "apiVersion is required") {
+	if !strings.Contains(msgs[2].Err.Error(), "apiVersion is required. The value must be either \"v1\" or \"v2\"") {
 		t.Errorf("Unexpected message 2: %s", msgs[2].Err)
 	}