travis-ci/travis-ci.github.com — pull request #313 by vterron (2013-08-09 11:25:50+00:00)
Title: Explain that Ubuntu 12.04 only includes Python 2.7 system packages

The docs clearly recommend not to relay on the Python system packages, but some users may still find them very useful — especially if the dependencies include lots of C code (NumPy, SciPy) that would take a long time to compile. Warn them that --system-site-packages only works in the Python 2.7 virtualenv.