Improve formatting multiple context managers

[smurfix]

ruff --format currently reformats this code:

async with \
        Dispatch(obj.cfg, run=True, sig=True) as dsp, \
        dsp.cfg_at(*cfg["path"], *cfg_path) as cf, \
        dsp.sub_at(*cfg["path"], *fs_path) as fs:

as

async with Dispatch(obj.cfg, run=True, sig=True) as dsp, dsp.cfg_at(
        *cfg["path"],
        *cfg_path,
    ) as cf, dsp.sub_at(*cfg["path"], *fs_path) as fs:

This is … really unhelpful. It would be a lot nicer to add parentheses instead:

async with (
    Dispatch(obj.cfg, run=True, sig=True) as dsp,
    dsp.cfg_at(*cfg["path"], *cfg_path) as cf,
    dsp.sub_at(*cfg["path"], *fs_path) as fs,
):

which I currently need to do manually.

This syntax refinement was added in Py3.10.

[charliermarsh]

Parenthesized context managers aren't supported on older versions of Python, but we will enforce this as part of implementing Black's preview style.

[MichaReiser]

I'll close this because it is tracked in #8678 (see wrap_multiple_context_managers_in_parens)