bench init with preferred Python EXEC for CI (#13336)

* bench_init.sh added python executable flag for environment setup

* Added future python build matrix

* udpate build matrix

* Update .travis.yml

* Update .travis.yml
diff --git a/.travis.yml b/.travis.yml
index 70df757..74ed7b7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,6 +3,11 @@
 
 python:
   - "2.7"
+  - "3.6"
+  
+ matrix:
+  - allow_failures:
+    - python: "3.6"
 
 services:
   - mysql