Ну, на самом деле ваш файл css
и html
необходимо обменять. Правильная структура должна быть:
BMEWebServer/appBMEWebServer.py
BMEWebServer/templates/index.html
BMEWebServer/static/style.css
I think I've figured it out, at least I think I do ( the client just keeps on uploading now, error-free ) . After you read data from a file that you upload, you should also CLOSE it. Who would have thought? :P