I don’t know Python, but i think it is because you don’t attach a MIME type to your videofile
field.
See here, for a similar issue in NodeJS: Best way to upload 30k videos? - #24 par GregRc
This seems to be done in the script mentionned by Chocobozzz, using this function:
def get_file(path):
mimetypes.init()
return (basename(path), open(abspath(path), 'rb'),
mimetypes.types_map[splitext(path)[1]])