// Generate package's info for build old course structure.
        private void BuildPackageInfoFile(long mediaOriginalSize, long mediaZippedSize)
        {
            PackageInfo pi = new PackageInfo();
            pi.PackagePath = this.lessonName + ".zip";
            pi.Size = mediaOriginalSize;
            pi.ZippedSize = mediaZippedSize;

            var mapfileContent = JsonConvert.SerializeObject(pi);

            // for every package alwasy use the same package name.
            // lesson_221.json
            var saveTo = this.constants.LocalMediaPath + @"\lesson_" + lesson.Id + ".pinfo";

            MapfileHelper.Save(mapfileContent, saveTo);
        }