Kevin Bullock <kbullock+mercurial@ringworld.org> [Mon, 23 Oct 2017 22:13:59 -0500] rev 34923
setup: filter out devel-warn messages from system hg
If we're going to use the user's installed and configured hg command
(which we do since 8b20338b989e), we should prevent devel-warn messages
from interfering with locating it.