One more attempt...

.travis.yml

@@ -1,16 +1,14 @@
 sudo: false
-language: python
 install: 
     - pip install tox
     - pip install cython
     - make cythonize
 script: 
     - tox -v
+language: python
 python:
-    - 2.7
+    - 3.5
 env:
     - TOXENV=coveralls DEPENDENCY_INJECTOR_DEBUG_MODE=1
-    - TOXENV=pylint
-    - TOXENV=flake8
-    - TOXENV=pydocstyle
+    - TOXENV=pylint,flake8,pydocstyle
     - TOXENV=py26,py27,py33,py34,py35,pypy,pypy3

tox.ini

@@ -9,7 +9,7 @@ commands=
     unit2 discover tests
 
 [testenv:coveralls]
-basepython=python
+basepython=python3.5
 passenv=TRAVIS TRAVIS_JOB_ID TRAVIS_BRANCH
 deps=
     {[testenv]deps}
@@ -22,14 +22,12 @@ commands=
     coveralls
 
 [testenv:pylint]
-basepython=python
 deps=
     pylint
 commands=
     - pylint -f colorized --rcfile=./.pylintrc dependency_injector
 
 [testenv:flake8]
-basepython=python
 deps=
     flake8
 commands=
@@ -37,7 +35,6 @@ commands=
     flake8 --max-complexity=10 examples/
 
 [testenv:pydocstyle]
-basepython=python
 deps=
     pydocstyle
 commands=