I had to modify path to static files in your example (static/SkylarkUpload/SkylarkUpload.css and static/SkylarkUpload/upload.js), but it works.
I think you should add some protection to this app:
- file size limit, now I can crush the app by uploading big file (>4GB on 32-bit system). Client side code (javascript) doesn't recognize this situation and after application restart shows "0%"
- upload directory total size limit
Is it possible to keep uploaded file parts on disk, not in RAM?
I can imagine situation when someone starts upload many times and doesn't finish it to make server run out of memory.