Fix Travis CI

Signed-off-by: Maciej Kurc <mkurc@antmicro.com>

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 08e83b0..c5e4270 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,15 +2,10 @@
 
 python:
   - 2.7
-    env: TOXENV=py27
   - 3.4
-    env: TOXENV=py27
   - 3.5
-    env: TOXENV=py27
   - 3.6
-    env: TOXENV=py27
   - 3.7
-    env: TOXENV=py27
 
 install:
   - source prepareenv.sh
@@ -20,7 +15,7 @@
 script:
   - conda activate yosys-env
   - which tox
-  - tox
+  - TOXENV="py${TRAVIS_PYTHON_VERSION//./}" tox
 
 notifications:
   email: false

tox.ini

diff --git a/tox.ini b/tox.ini
index 002e79f..2d6aad1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,6 +5,8 @@
 setenv =
     PYTHONPATH={toxinidir}/v2x
 basepython =
+    py27: python2.7
+    py34: python3.4
     py35: python3.5
     py36: python3.6
     py37: python3.7
@@ -16,6 +18,7 @@
     pytest
 commands =
     check-manifest --ignore tox.ini,tests,*.pyc
+    python --version
     # This repository uses a Markdown long_description, so the -r flag to
     # `setup.py check` is not needed. If your project contains a README.rst,
     # use `python setup.py check -m -r -s` instead.