www/py-cheroot: Update to 6.5.6

• There is currently a signification amount of version churn in the upstream repository so use the most recent signed release for now.

• Since release 6.3.0 the port installs a CLI tool outside the Python environment thus make it concurrent safe.

• Also backport two patches to retain compatibility with recent versions of devel/py-setuptools and avoid failures at runtime with Python 3 while I'm here. [1]

Changelog since 6.0.0:

https://github.com/cherrypy/cheroot/blob/v6.5.6/CHANGES.rst

PR: 241369
Submitted by: Keith Gaughan <k@stereochro.me> (maintainer)
Approved by: Keith Gaughan <k@stereochro.me> (maintainer) [1]
MFH: 2019Q4