bpo-38468 : Refactor python-config (#16749)

* refactor python-config

* 📜🤖 Added by blurb_it.

* Update Misc/NEWS.d/next/Build/2019-10-13-16-18-24.bpo-38468.buCO84.rst

Co-Authored-By: Pablo Galindo <Pablogsal@gmail.com>

* Use getvar for pyver

* Update news entry with affected file.

* Update Misc/NEWS.d/next/Build/2019-10-13-16-18-24.bpo-38468.buCO84.rst

Co-Authored-By: Victor Stinner <vstinner@python.org>

* Update 2019-10-13-16-18-24.bpo-38468.buCO84.rst