print() is a function in Python 3

.travis.yml

@@ -10,14 +10,22 @@
 language: python
 python:
   - "2.7"
-  - "3.5"
-
-# command to install dependencies
-install: "pip install -r common/requirements.txt"
+  - "3.6"
 
 # if we don't need sudo we can run in containers
 sudo: false
 
+# command to install dependencies
+install:
+  - "pip install -r common/requirements.txt"
+  - pip install flake8
+
+before_script:
+  # stop the build if there are Python syntax errors or undefined names
+  - flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
+  # exit-zero treats all errors as warnings.  The GitHub editor is 127 chars wide
+  - flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+
 # test common
 script: nosetests --where common ccm.common