Drop Python 3.6 support (for running Black only)

[ichard26]

The current consensus is to remove Python 3.6 support for running Black as part of 22.9.0 (or 22.10.0, not sure when the next release after 22.8.0 is happening) (September/October 2022). Here's what needs to be done:

• Clean-up our asyncio code with the QOL features added in 3.7 (cc @graingert and @zsol when 2023 is closer)
• Remove Python 3.6 from CI and CD (i.e. mypyc wheel build automation)
• Remove Python 3.6 from setup.py (metadata, etc.)
  • Remove the dataclasses backport dependency since 3.7+ always has it
  • Update the assert sys.version_info >= (3, 6, 2), "black requires Python 3.6.2+" check
• Maybe try running pyupgrade --py37-plus ...?
• Maybe remove the "patch click to not die on LANG=C" code ...? I can't remember whether we can do once 3.6 or 3.7 is dropped.

P.S. co-maintainers, please edit this issue if you remember some other thing we need to do. My memory is hazy.

[ichard26]

Update, the next release after 22.8.0 (#3163) will drop 3.6 support (for running Black only). It's undecided whether the next release will happen in September or October, so the milestone mayyy be a month early.

We decided that keeping 3.6 support after it's been EOLed for a while doesn't really make sense anymore since folks still using 3.6 can probably upgrade to 3.7 (having not already because "it just works", it being their CI systems or whatever) or are using a rather old version of Black (like the ever-popular 21.8b1 🤨).

We really want to switch to Hatch (from setuptools) and dropping 3.6 support is prerequisite to that.

[ddelange]

fwiw starting from black 22.10.0, installing from source (in my case the pre-commit hook) is already not supported anymore on py3.6, due to hatchling>=1 being py3.7+:

ERROR: Could not find a version that satisfies the requirement hatchling>=1.8.0 (from versions: 0.8.0, 0.8.1, 0.8.2, 0.9.0, 0.10.0, 0.11.0, 0.11.1, 0.11.2, 0.11.3, 0.12.0, 0.13.0, 0.14.0, 0.15.0, 0.16.0, 0.17.0, 0.18.0, 0.19.0, 0.20.0, 0.20.1, 0.21.0, 0.21.1, 0.22.0, 0.23.0, 0.24.0, 0.25.0, 0.25.1)
ERROR: No matching distribution found for hatchling>=1.8.0

[ichard26]

That's... intentional? 22.10.0 doesn't support Python 3.6 at all as planned. It is confusing to keep this issue open though, so I'll close it.