conflicts.add(String.format(
                            "Conflicting extension %s: %s vs %s",
                            key,
                            formatLocation(conflict.getLocation("")),
                            formatLocation(coreExtension.getLocation(""))));
                }
            }
        }
        if (!conflicts.isEmpty()) {

     *            to force output of model id and source.
     * @return The formatted problem location or an empty string if unknown, never {@code null}.
     */
    public static String formatLocation(ModelProblem problem, String projectId) {
        StringBuilder buffer = new StringBuilder(256);

        if (!problem.getModelId().equals(projectId)) {
            buffer.append(problem.getModelId());

        StringBuilder buffer = new StringBuilder(128);

        buffer.append('[').append(getSeverity()).append("] ");
        buffer.append(getMessage());
        buffer.append(" @ ").append(ModelProblemUtils.formatLocation(this, null));

        return buffer.toString();
    }

            writer.print(problem.getSeverity());
            writer.print("] ");
            writer.print(problem.getMessage());
            writer.print(" @ ");
            writer.println(ModelProblemUtils.formatLocation(problem, modelId));
        }

        return buffer.toString();
    }