build: issue2551397: remove support for python 3.6 3.7 ci build works. Make changes to make 3.7 current minimum supported version. Also removed some references that apply only when running under 2.7.

#!/usr/bin/env python
from __future__ import print_function
import zlib, base64, sys
print(base64.encodestring(zlib.compress(sys.stdin.read())))