Travis: multiple Python environments.

.travis.yml

@@ -1,13 +1,22 @@
+# To mimic README.md installation and hacking instructions as much as
+# possible, this config file instructs Travis CI to create a build
+# environment for each supported Python version, and then for each of
+# those it runs tox with two environments: lint and pyXX corresponding
+# to the currently used Travis CI build Python version.
+
 language: python
 
+python:
+  - "2.6"
+  - "2.7"
+
 before_install: >
   travis_retry sudo apt-get install python python-setuptools 
   python-virtualenv python-dev gcc swig dialog libaugeas0 libssl-dev
 
-install: travis_retry python setup.py dev[testing]
+install: travis_retry python setup.py dev[testing]  # installs tox
 script: travis_retry tox
 
 env:
-  - TOX_ENV=py26
-  - TOX_ENV=py27
+  - TOX_ENV=py${TRAVIS_PYTHON_VERSION//[.]/}
   - TOX_ENV=lint