Drop support for Python v3.8 and remove asgiref from non Django code

[medihack]

As discussed on Discord, we want to drop support for Python v3.8 as it reached its end-of-life. We then can use asyncio.to_thread (available in Python >= 3.9) instead of asgiref.sync.sync_to_async (we should then do this together in the 3.0 release).

[medihack]

I took a quick look at replacing asgiref.sync_to_async with asyncio.to_thread, but I don't think it is worth it. We use sync_to_async quite often as a decorator, which is not directly possible with asyncio.to_thread. And asgiref also has the convenient method the other way around (async_to_sync).

[onlyann]

I think it is more nuanced than that.

asgiref might need to stay for the Django integration as per their async doc.

However, there is no need to make it a dependency for any consumer that is not using Django.

We use sync_to_async quite often as a decorator, which is not directly possible with asyncio.to_thread

That should be fine. Beside Django integration, it seems it is only used in tests. That could stay there or it would be trivial to update to not use a decorator and explicitly wrap the function.

[medihack]

Ok, good point. I will give it a try.

[ewjoachim]

So shall I close this as #1224 was merged or do we keep it open for the replacement of sync_to_async ?

[medihack]

So shall I close this as #1224 was merged or do we keep it open for the replacement of sync_to_async ?

PR #1226 will close it :-)