Python 3.10 Readiness

[nateprewitt]

Python 3.10 is just a little over a month away and we have some issues that need to be addressed in Requests. Currently our test suite relies heavily on httpbin which has been largely unmaintained since 2017. As a dependency, it relies on brotlipy which has since migrated to a new package brotlicffi. Given these are both C-based, we can't compile them in CI environments and rely on wheels being available.

It looks unlikely that we'll get a new wheel for brotlipy, so we'll need to either find a way to migrate httpbin to brotlicffi, or work out another alternative for the test suite. I still have PyPI credentials for httpbin to cut a new release, but there's a matter of ownership to be worked out now that it's under Postmanlabs. It also appears to have several versions in the commit history that have never been published that we'll need to consider.

[sigmavirus24]

I was removed from httpbin when it was sold/transferred to Postman. Maybe it's time to fork/use something different? #5915 has the start of something we might be able to use instead

[sethmlarson]

@nateprewitt I can get you a new wheel of brotlipy for Python 3.10. I've never built a wheel from a build candidate however. Is the way to go there to build a wheel from a build candidate and then once Python 3.10 is officially released upload a new wheel for 3.10 with an incremented build number? If that works for you I can take care of that step.

[nateprewitt]

If we can push a new wheel from the brotlipy tag, that may be much easier than the alternatives in the short term. I would assume the wheels would be virtually identical between the rc and official release. If we have issues though, we can definitely revisit updating the build number with a wheel from the official 3.10 release. Thank you!!

[sethmlarson]

Uploaded abi3 wheels for brotlipy which are compatible with Python 3.10 and all future Python 3 versions: https://twitter.com/sethmlarson/status/1433488043529359369

[nateprewitt]

Now that @sethmlarson has been kind enough to get us unblocked, I think we should be set with #5928.

[theGOTOguy]

@sigmavirus24 If it's decided that #5915 is the future of requests' testing, I will refactor all of the tests to use it and then remove the existing test server.