Log Message:
py-virtualenv: updated to 16.1.0

16.1.0:
Fixed documentation to use pypi.org and correct curl options
bug fix: ensure prefix is absolute when creating a new virtual environment
upgrade setuptools from 39.1.0 to 40.5.0
upgrade wheel from 0.31.1 to 0.32.2
upgrade pip from 10.0.1 to 18.1
activate.csh does not use basename and handles newlines
fix failure to copy on platforms that use lib64
enable tab-completion in the interactive interpreter by default, thanks to a new \ 
sys.__interactivehook__ on Python 3
suppress warning of usage of the deprecated imp module