BUG: Removing LANG env causes issues

The PR https://github.com/docker-library/python/pull/570 causes several issues

> python:3.8 either falls apart to UnicodeEncodeErrors in cause of 'ascii' not knowing about utf-8 characters 

## Quick Fix

Users can set `ENV LANG=C.UTF-8` in their Dockerfiles