*
     * @param model The model to create a source hint for, may be {@code null}.
     * @return The user-friendly source hint, never {@code null}.
     */
    static String toSourceHint(Model model) {
        if (model == null) {
            return "";
        }
        StringBuilder buffer = new StringBuilder(128);
        buffer.append(toId(model));
        Path pomPath = model.getPomFile();

                problems.add(
                        Severity.ERROR,
                        ModelProblem.Version.BASE,
                        "Invalid packaging for parent POM " + ModelProblemUtils.toSourceHint(parentModel)
                                + ", must be \"pom\" but is \"" + parentModel.getPackaging() + "\"",
                        parentModel.getLocation("packaging"));
            }
        }