bug 1186235 - Set VIRTUALENV_EXISTS when calling taskcluster-npm-cache-get. r=jgriffin.
bug 1186235 - Set VIRTUALENV_EXISTS when calling taskcluster-npm-cache-get. r=jgriffin.

mozilla/build-mozharness,lissyx/build-mozharness,mozilla/build-mozharness,lissyx/build-mozharness