Travis special requirements for each python version

Travis CI adds an environment variable called $TRAVIS_PYTHON_VERSION that can be referenced in your .travis.yml:

python:
  - 2.6
  - 2.7
  - 3.2
  - 3.3
  - pypy
install:
  - if [[ $TRAVIS_PYTHON_VERSION == 2.6 ]]; then pip install importlib unittest2; fi
  - pip install -r requirements.txt

This would cause unittest2 and importlib to be installed only for Python 2.6, with requirements.txt being installed for all versions listed. You can do as many of these checks as necessary. Tornado’s .travis.yml file uses it quite a bit.