Address breakage of our test suite *before* aiohttp 4.0.0 goes out of alpha

[ichard26]

So thanks to the various dependency related fires we've had lately, I've created ichard26/black-deps-ci which runs Black's test suite using the latest development versions for most of our dependencies (exceptions being subdependencies and most of the test dependencies) *daily*

Turns out there's a lot of overrides necessary for CI to be green. Python 3.6 support being dropped is responsible for the vast majority of overrides, but on the other hand, aiohttp breaks our test suite as the aiohttp.test_utils.unittest_run_loop decorator was removed 🙃

https://github.com/ichard26/black-deps-ci/blob/4e25ac3dea340a956e35dab37b2ac5c4177c105e/generate.py#L9-L24

overrides = {}
overrides["aiohttp"] = [
    ("aiohttp>=3.7.4 ; python_version == '3.6'", "aiohttp 4.x requires Python 3.7+"),
    ("aiohttp<4", "aiohttp 4+ breaks our test suite as @unittest_run_loop was deleted"),
]
overrides["click"] = [("click>=8.0.0 ; python_version == '3.6'", "click 8.1.0+ dropped Python 3.6 support")]
overrides["ipython"] = [
    (
        "ipython>7.8.0 ; python_version <= '3.7'",
        "ipython 7.17+ dropped Python 3.6 and ipython 8+ dropped Python 3.7 support",
    )
]
overrides["pytest"] = [("pytest>6.1.1 ; python_version == '3.6'", "pytest 7.1.0+ dropped Python 3.6 support")]
overrides["platformdirs"] = [("platformdirs>=2 ; python_version == '3.6'", "platformdirs 2.5.1< dropped Python 3.6 support")]
overrides["tokenize-rt"] = [("tokenize-rt>3.2.0 ; python_version == '3.6'", "tokenize-rt 4.2.1< dropped Python 3.6 support")]
overrides["tomli"] = [("tomli>=1.1.0 ; python_version == '3.6'", "tomli 2.0.0+ dropped Python 3.6 support")]

And FYI, we've been warned about this in CI: https://github.com/psf/black/runs/5727523727?check_suite_focus=true#step:6:325

---

The best solution is probably to allow the import to fail replacing unittest_run_loop with just a no-op decorator. Although I wouldn't object to bumping up our aiohttp lower bound.

[ichard26]

It's worth noting even though a substantial amount of our dependencies have removed Python 3.6 support, we will (probably) be fine keeping it for quite a bit longer as our lower bounds are still low enough where pip will be able to install something functional.