zuul-jobs/roles/ensure-virtualenv/README.rst

Ensure virtualenv is available

This role installs the requirements for the virtualenv command on the current distribution.

Users should be aware of some portability issues when using virtualenv:

• Distributions differ on the interpreter that virtualenv is provided by, so by calling virtualenv with no other arguments means that on some platforms you will get a Python 2 environment and others a Python 3 environment.
• If you wish to call virtualenv as a module (e.g. python -m virtualenv) you will need to know which interpreter owns the virtualenv package for your distribution; e.g. on some, such as Bionic, virtualenv is provided by python3-virtualenv but python refers to Python 2, so python -m virtualenv is not a portable way to call virtualenv.
• virtualenv -p python3 is likely the most portable way to consistently get a Python 3 environment. virtualenv -p python2 may not work on some platforms without Python 2.
• If you use Python 3 and do not require the specific features of virtualenv, it is likely easier to use Python's inbuilt python3 -m venv module to create an isolated environment. If you are using pip: in your Ansible roles and require an environment, see the documentation for :zuulensure-pip.