By including one or more Project-URL entries in PKG-INFO metadata,
PyPI can display helpful hyperlinks in a generic manner. Add support
here to be able to pass it through setup.cfg and setup.py with a
project_urls dict. See the corresponding section of the Core
Metadata Specifications from the Python Packaging User Guide for
details:

https://packaging.python.org/specifications/core-metadata/#project-url-multiple-use

use ssl.create_default_context and SNI if available

Build meta: fixes and cleanups

Fix test command

support `setup_requires` in setup.cfg

python 3 bdist_egg --exclude-source-files __pycache__ issue