The `virtualenvwrapper` script has been relocated to
`/usr/local/bin/virtualenvwrapper.sh`. Update the
plugin to look in the new location first. See:

http://virtualenvwrapper.readthedocs.io/en/latest/#introduction

to confirm the change in location for this script.

This addresses issue #3047 where the solution was to source this file
from your zshrc.