Currently, virtualenv is a separate application, allowing virtualization of Python installations. For Python 3.3, a built-in mechanism is being developed. The objective of this project is to come up with a test suite for this virtualization mechanism.
Important background information to review if proposing to work on this:
Distutils-SIG mailing list threads mentioning "pythonv," beginning with "early preview of pythonv."
The work-in-progress repository at Bitbucket and its open issues.
This PyCon presentation on how virtualenv works.