Run tests against Python 2 and 3 versions in circleci

circle.yml

@@ -1,4 +1,17 @@
+machine:
+  environment:
+    TOX_PY27: '2.7.10'
+    TOX_PY35: '3.5.0'
+
+dependencies:
+  override:
+    - pip -V
+    - pip install -U pip
+    - pip install -U ipdb
+    - pip install -U tox
+    - pip install -U tox-pyenv
+    - pyenv local $TOX_PY27 $TOX_PY35
+
 test:
   override:
-    - python setup.py test
-    - ./contrib/test_build.sh
+    - tox -v --recreate

tox.ini

@@ -0,0 +1,14 @@
+[tox]
+envlist = py27,py35
+
+[testenv]
+whitelist_externals = env
+                      source
+                      bash
+install_command = pip install -U {opts} {packages}
+setenv = TOX_ENV_NAME={envname}
+passenv = TOX_* TRANSIFEX_USER TRANSIFEX_PASSWORD
+commands = python -V
+           env
+           python setup.py test
+           bash ./contrib/test_build.sh