test: disable the new style rendering for "missing parent"
The style kicks in when we display a partial tree. Supporting test running both
3.7 and default with this is painful, we disable the new feature for now.
#require test-repo pyflakes
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:**.py or grep("^!#.*python")' 2>/dev/null \
> | xargs pyflakes 2>/dev/null