feat: add support for Python 3.9, 3.10 and 3.11

[paul-finary]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Related Issue	Fix #549, Fix #551
Need Doc update	yes

Describe your change

This PR removes support for python 2.7, adds support for python 3.11 and tests the project against 3.9, 3.10, and 3.11:

• Replaced all @asyncio.coroutine decorators by async def function def
• Replaced yield from with await or return statements
• Added python 3.9, 3.10, and 3.11 to tox and circleci

What problem is this fixing?

Due to a removed syntax in python 3.11, the package was not working.

[paul-finary]

Hi @shortcuts , I opened this PR because the other one (#551) is stale for 3 weeks now. However the tests are failing on circleci even though they're all passing locally. Do you have any idea ?

[paul-finary]

Hi @shortcuts,
Sorry to insist, but did you have a look at this PR ?

[paul-finary]

Hi again,

Can someone look at this PR ?

[shortcuts]

hey, checking right now for the CI! thanks for the contribution :)

[shortcuts]

looks great! small comment

still trying to figure out the CI issue, not sure if it's related to the fork 🤔

[paul-finary]

looks great! small comment

Hi, I fixed both comments :)

[paul-finary]

Hi, there' still issues with the pipelines even thought the tests are running locally, do you have an idea on how to solve it ?

[shortcuts]

hey @paul-finary, fixed the CI so it should now properly run and report errors, let me know if you still have time to work on that

[shortcuts]

fixed some more again, should be more reliable now, still some flaky ones but there seems to be errors related to yield inside async fns

[shortcuts]

seems like everything is covered, I'll do an other pass and plan the release ASAP