Add error wrapping for predictor model key (#867)

(cherry picked from commit 7460edf)

Author: deliahu

pkg/operator/operator/validations.go

@@ -492,7 +492,7 @@ func validateTensorFlowPredictor(predictor *userconfig.Predictor) error {
 
 	awsClient, err := aws.NewFromEnvS3Path(model)
 	if err != nil {
-		return err
+		return errors.Wrap(err, userconfig.ModelKey)
 	}
 
 	if strings.HasSuffix(model, ".zip") {
@@ -502,7 +502,7 @@ func validateTensorFlowPredictor(predictor *userconfig.Predictor) error {
 	} else {
 		path, err := getTFServingExportFromS3Path(model, awsClient)
 		if err != nil {
-			return err
+			return errors.Wrap(err, userconfig.ModelKey)
 		} else if path == "" {
 			return errors.Wrap(ErrorInvalidTensorFlowDir(model), userconfig.ModelKey)
 		}
@@ -521,7 +521,7 @@ func validateONNXPredictor(predictor *userconfig.Predictor) error {
 
 	awsClient, err := aws.NewFromEnvS3Path(model)
 	if err != nil {
-		return err
+		return errors.Wrap(err, userconfig.ModelKey)
 	}
 
 	if ok, err := awsClient.IsS3PathFile(model); err != nil || !ok {