io

I'm opening this issue prepared to be declared blind and pointed at the relevant bit of documentation, but I've looked far and wide, and it's definitely not in this repo, not in a form that a grep can find.

What should happen if deliver_cancel raises an exception? In the current implementation, the shielded cancel scope will prevent it from propagating until the process exits, which might take a while if the crash occurred before signaling the process in any way. Maybe on exception from a user-specified deliver_cancel we should call the default deliver_cancel to kill the process? Or just kill() since

PyTorch core has download function and torch.hub.download_url_to_file.
Torchaudio can use it for dataset download and does not need to maintain its own torchaudio.datasets.utils.download_url.

In addition to that, there seems to be something wrong with torchaudio.datasets.utils.download_url.
It fails to download multiple of huge files. I think we should get rid of `torchaudio.datasets.ut