Update wercker.yml

wercker.yml

@@ -6,7 +6,7 @@
 # If you want Google's container you would reference google/python
 # Read more about containers on our dev center
 # https://devcenter.wercker.com/overview-and-core-concepts/containers/
-box: python:3.x
+box: python:3.1
 # You can also use services such as databases. Read more on our dev center:
 # https://devcenter.wercker.com/administration/services/
 # services: