v31.2.3

This is a bugfix release.

There is a fix for an installation issue with the new "packaging" version 22.0.
This is replaced by a fork named "packvers" to work around
pypa/packaging#530 and provide an emergency
fix for #3171 and #3177

We updated these dependencies:

• https://github.com/nexB/pip-requirements-parser
• https://github.com/nexB/dparse2/

With the new:

• https://github.com/nexB/packvers/

We also improved the compatibility for pre-built wheels and now build one
wheel for each Python version to work around some Python pickle bug.

We pinned SPDX tools for cope with the upcoming API breaking changes.

Full Changelog: v31.2.1...v31.2.3