* @return the path to the JAR file
     * @throws ThemeException if the JAR file does not exist
     */
    protected Path getJarFile(final Artifact artifact) {
        final Path jarPath = ResourceUtil.getPluginPath(artifact.getFileName());
        if (!Files.exists(jarPath)) {
            throw new ThemeException(artifact.getFileName() + " does not exist.");
        }
        return jarPath;
    }