Comment 11 for bug 767205

Also twisted.web.client now has a FileBodyProducer which did not exist when I started my branch. I do not plan on continuing with agent-767205 but starting fresh (using FileBodyProducer from twisted if available). Concerning MD5, since this is optional to s3 so far as I an tell, I'd like the interface also to not require this - but allow it to be passed optionally in cases where it is known upfront.