compat: drop support for Mercurial 4.2
Since Mercurial 4.6 is about to be released, we drop support for 4.2 too.
(code still need to be cleaned up).
#require test-repo
$ checkflake8() {
> if ! (which flake8 > /dev/null); then
> echo skipped: missing tool: flake8;
> exit 80;
> fi;
> };
$ checkflake8
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run flake8 if it exists; if it doesn't, then just skip
$ hg files -0 'set:(**.py or grep("^#!.*python")) - removed()' \
> -X hgext3rd/evolve/thirdparty \
> 2>/dev/null \
> | xargs -0 flake8