First, install tox into your virtualenv:
pip install -U tox
To run all the qrcode tests, you'll need to install the older Python interpreters. Here's how you'll do it on a modern Ubuntu distribution:
sudo add-apt-repository ppa:fkrull/deadsnakes sudo apt-get update sudo apt-get install python2.4-dev python2.6-dev
Ensure you have the libraries to build PIL, too:
sudo apt-get install build-essential python-dev python3-dev sudo apt-get install libjpeg8-dev zlib1g-dev
Finally, just run tox!
If you want, you can test against a specific version like this: tox -e py33