[#4942] Gracefully handle bad / missing tools
Forward-ported from https://sourceforge.net/p/allura/git/merge-requests/9/
Signed-off-by: Cory Johns johnsca@geek.net
Authored by: Cory Johns 2012-10-26
Committed by: Dave Brondsema 2012-10-26
Parent(s): [cf03d3]
Child(ren): [4fdcdd]
