Add a python 2.7 compatibility checker to dvp build

[fdrozdowski]

Given that 2.7 support for python is going away I think it will be good to have validation to make sure users do not have python 3 incompatible code in their plugins.

This is likely a post GA type task but I think adding warnings will greatly help transition for SDK users once we do the work to drop python 2.7 support.

┆Issue is synchronized with this Jira Story by Unito