Solve static files deadlock bug for django 3.0+ (#1722)

[sterliakov]

#1722
With Django 3.0 and newer we have native ASGI handler. This fast fix removes annoying deadlock exception for development server. I saw we shouldn't focus on it and have to rewrite this part using Django native capabilities, but it can work as temporary simple fix.

[dr-luke]

This is a decent fix for this problem, I just made a comment on a thread about how people could monkey patch their django installs temperately to avoid this issue until a more permanent fix is approved. Thank you for your contribution, cheers.

[LiteWait]

Pardon my ignorance. I am running Django 3.2, does this imply I can throw away channels==3.0.4 in favor of something else?

"With Django 3.0 and newer we have native ASGI handler. This fast fix removes annoying deadlock exception for development server. I saw we shouldn't focus on it and have to rewrite this part using Django native capabilities, but it can work as temporary simple fix."

[ktosiek]

@LiteWait the native ASGI handler only replaces one part of Channels: adapting Django middleware/views system to ASGI. You still need channels if you have any Consumers in your app.

[ktosiek]

@sterliakov have you tested this on Django 2.2 (which is current minimum for Channels)? I don't think it calls get_response_async.

[carltongibson]

Django 3.2 will be the minimum required version going forward.

[JulienPalard]

Tested using Django 4.0.5, looks like to solve the issue.

[carltongibson]

Yes, but this will be removed in favour of Django's own ASGIStaticFilesHandler for the next release.

[carltongibson]

Superseded by #1890.