License-expression

--------------------

This is a minor release without API changes:

- Use latest skeleton
- Update license list to latest ScanCode and SPDX 3.23
- Drop support for Python 3.7

--------------------

This is a minor release without API changes:

- Use latest skeleton
- Update license list to latest ScanCode and SPDX 3.22
- Add Python 3.12 support in CI

----------------------

This is a minor dot release without API changes

- Use latest skeleton
- Update license list to latest ScanCode and SPDX 3.20

----------------------

This is a minor release without API changes

- Use latest skeleton (and updated configure script)
- Update license list to latest ScanCode and SPDX 3.19
- Use correct syntax for python_require
- Drop using Travis and Appveyor
- Drop support for Python 3.7 and add Python 3.11 in CI

----------------------

This is a minor release with API changes

- Use latest skeleton (and updated configure script)
- Drop using calver
- Improve error checking when combining licenses

----------------------

Added
~~~~~

- Switch to calver for package versioning to better convey the currency of the
bundled data.

- Include https://scancode-licensedb.aboutcode.org/ licenses list with
ScanCode (v21.6.7) and SPDX licenses (v3.13) keys. Add new functions to
create Licensing using these licenses as LicenseSymbol.

- Add new License.dedup() method to deduplicate and simplify license expressions
without over simplifying.

- Add new License.validate() method to return a new ExpressionInfo object with
details on a license expression validation.


Changed
~~~~~~~
- Drop support for Python 2.
- Adopt the project skeleton from https://github.com/nexB/skeleton
and its new configure script