After following the instructions on Doug Hellman\'s virtualenvwrapper post, I still could not fire up a test environment.
[mpenning@tsunami ~]$ mkvirtualenv
Using Git Bash on Windows 10 and Python36 for Windows I found the virtualenvwrapper.sh in a slightly different place and running this resolved the issue
source virtualenvwrapper.sh /c/users/[myUserName]/AppData/Local/Programs/Python36/Scripts