don't `apt-get install python-virtualenv` use `pip install virtualenv` because `pip` installs latest version, else you are under distro's package maintainer's mercy for update. After `python setup.py publish` only distro's package is updated.
EDIT: Using pip can simply solve py3 and py2 specific features.
There's an argument there - do you want to be at your distro's security update mercy, or have to remember/have two separate sets of security patch processes to run through?
EDIT: Using pip can simply solve py3 and py2 specific features.