black: rename pyproject.toml to black.toml Black won't read this automatically (you'll have to specify --config), but having a pyproject.toml *at all* puts pip in PEP 517/518 mode which breaks us for obscure reasons I don't understand. Rather than waste a ton of time fighting with pip, let's just do this. Differential Revision: https://phab.mercurial-scm.org/D7087

fix: remove a never-true check for unset pattern in Fixer.affects() We don't create an instance of a Fixer if the pattern is None, so we don't need to check that in affects(). Differential Revision: https://phab.mercurial-scm.org/D7086

fix: warn when a fixer doesn't have a configured command It seems we currently produce an empty command line and then decide to not run it, but it seems better to skip that part too. Differential Revision: https://phab.mercurial-scm.org/D7085

fix: make Fixer initialization more explicit for clarity I found it quite confusing that Fixer accessed fields that seemed like they didn't exist. Differential Revision: https://phab.mercurial-scm.org/D7084

fix: don't pass in default value when looking up config The defaults are now registered correctly so we don't need to pass in the default value when we look up a config value. Differential Revision: https://phab.mercurial-scm.org/D7083

fix: fix registration of config item defaults Before this patch, because of the "(:<name>)?", all registered patterns would match and the default value would not be the one we thought we had registered (maybe it just took the default value for the first match?). This didn't matter because we didn't care about the default value; we used our own, intended default value in getfixers() anyway. We also have to look up each config item individually in order to not get developer warnings. Differential Revision: https://phab.mercurial-scm.org/D7082

automation: capture additional exception when formatting I started encountering this for some reason. Differential Revision: https://phab.mercurial-scm.org/D7078

contrib: update to latest Windows package versions Let's keep modern. Differential Revision: https://phab.mercurial-scm.org/D7077

rust-cpython: drop direct dependency on python(27|3)_sys We no longer use it.

rust-cpython: leverage upstreamed py_capsule_fn!() macro