bug 898711 - land _post_fatal() changes from beagle branch. r=rail
bug 898716 - land virtualenv changes from beagle branch. r=rail
bug 898715 - land script.py changes from beagle branch. r=rail
bug 898714 - land mercurial changes from beagle branch. r=rail
Merge remote-tracking branch 'origin/master' into beagle

Conflicts:
	mozharness/base/log.py
	mozharness/base/vcs/mercurial.py