packaging: fix docker-centos5 - use pythonexe and set to "python" as before Fix 92a51a45d44c .

packaging: move dockerrpm output directory creation to dockerrpm Avoid having to compute the directory in two places in different environments.

packaging: drop "support" for unsupported Fedora versions Fedora 31 has just been released, and Fedora 29 will be EOL in a month. Don't spend any time thinking about dead stuff.

mail: black wants to add this blank line I can't figure out how this got overlooked on previous runs, but here we are. It looks like the culprit change is already public?

hghave: verify we have a black that is new enough for our format We require what is currently the absolute latest black, so let's be paranoid.

contrib: fix up example fix configuration for our move to released black

phabricator: use True primitive instead of b'true' for phabupdate actions Something I'd missed in the creatediff port. This didn't matter before with the old PHP form style wireformat, but breaks with the new arcanist format. Differential Revision: https://phab.mercurial-scm.org/D7152

setup: allow py3 install without env vars 5.2 is the first release of Mercurial where py3 support is expected to be widely used, therefore we should allow installing it without hoop-jumping. Differential Revision: https://phab.mercurial-scm.org/D7151

formatting: drop `grey`, our custom black version Now that the official black has all we want, we can drop this.

formatting: using black to check for formatting