Drop support of Python 3.7

[loechel]

Remove Python 3.7 from list of supported Python Versions, as of today (2023-10-07) Python 3.7 is already end of Life (since 2023-06-27). See https://devguide.python.org/versions/ for reference.

See also #200.

[dataflake]

I am fine with merging this PR because all it does is change the drop-legacy-python script. I don't know anyone who uses that script after Python 2 support has been removed...

[icemac]

This script has to be adapted to be useable to actually drop Python 3.7 support. It was already used on all zopefoundation packages to drop Python 2.7 to 3.6 support, so this part is no longer needed and the change log messages should not mention it any more.

But really dropping Python 3.7 support also means to adapt all the templates and remove 3.7 from tox.ini, the c code build scripts etc.

[icemac]

Maybe the script should be reworked into one adding support for new version (aka 3.12) + the already existing dropping of outdated versions.

[tseaver]

If for nothing else than a tiny contribution to reducing our carbon footprint, can we please quit doing CI on EOL Python versions as a matter of policy? Under current rules, that would give us five "stable" Python versions to test, plus the one in alpha/beta for the succeeding release.

[dataflake]

I think the time has come to rework the templates in order to get rid of Python 3.7. I'm going to extend this PR soon.

[dataflake]

@icemac I have removed references to the drop-legacy-python.py script from the Readme.

[icemac]

@icemac I have removed references to the drop-legacy-python.py script from the Readme.

@dataflake Do you envision to no longer to use drop-legacy-python.py or should it become part of the ususal update config run?

[dataflake]

I don't use that script, for me the only use would be as a scripting example.

[mauritsvanrees]

For completeness sake: this is fine from a Plone standpoint.
Plone 6.0 supports Python 3.8-3.12, and Plone 6.1 (expected in Summer 2024) supports Python 3.10-3.12.