adding python to travis
diff --git a/.travis.yml b/.travis.yml
index 31bf190..16039e2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,7 +22,7 @@
       jdk:
         - oraclejdk8
     - language: python
-      python: 3.7
+      python: 3.6
 cache:
   directories:
   - "$HOME/.m2"