Specify the python versions for the environment explicitly CTR
diff --git a/.travis.yml b/.travis.yml
index c9bc45e..b1ec701 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,6 +3,9 @@
   - linux
 jdk:
   - openjdk8
+python:
+  - "2.7.15"
+  - "3.6.7"
 sudo: required
 dist: xenial
 services: