asyncio error code does not handle connection lost properly

[Skylion007]

When using s3fs, I saw this concerning message in the logs:

Future exception was never retrieved
future: <Future finished exception=ConnectionError('Connection lost')>
aiohttp.client_exceptions.ClientOSError: [Errno 32] Broken pipe

The above exception was the direct cause of the following exception:

ConnectionError: Connection lost

Luckily, I was using s3fs to output model checkpoints for training a deep learning model, and the next checkpoint succesfully saved, however, we should really probably properly handle this exception by either forwarding it to the caller, or alternatively, engaging in a low level retry to restore the connection and resume the upload.

[martindurant]

Did this actually involve a failed connection or transfer, or is it something that happens for example during interpreter shutdown? As far I know, all connections should be awaited, although I can imagine that in some cases a timeout (with associated error) might happen first.