-------------------
- Ignore unreleased Python versions (3.8 at the moment).
- Allow half-open ranges like ``--expect 3.5-``.
- Add experimental support for updating supported Python versions in
setup.py, tox.ini, .travis.yml, appveyor.yml and .manylinux-install.sh:
- command-line options --add and --drop to add and/or drop specific versions
- command-line option --update to explicitly enumerate all supported versions
- all changes are shown as diffs with confirmation before applying
- command-line option --diff to show the diffs and exit without any prompting
- command-line option --dry-run to re-run the parser and checker on in-memory
copies of updated files, to see if the update would succeed
- command-line option --only to limit the checks/update to some of the
supported files