Remove support for building python2 environments
This PR removes package references for Python <3.6 and removes support for building Python 2.7 environments.
Once deployed to testing
, the igwn-py27-testing
environment will be removed.
Once deployed to master
, the igwn-py27-proposed
environment will be removed.
The igwn-py27
stable environment and igwn-py27-YYYYMMDD
dated environments (oldstable) should remain to support legacy use.