python: increase the required python version

What:

Currently, all our python modules and programs only request python 3.11 or later. Python 3.11 is old, now.

Even if there still are security releases, it's going to be a limiting factor to stick with that old a version. It's time to increase the required version.

Expected:

The python code requires a python version that:

• is still maintained,
• brings interesting features (very subjective),
• gives enough time before we need to update again,
• is widely available in common systems (e.g. Debian, Ubuntu, Fedora).

Proposal:

Increase requirement to python version 3.14 or later:

• it is the latest stable version
• it will have generic bug fixes until 2027-10-05
• it will have security fixes until 2030-10-01
• it is widely available:
  • Ubuntu 26.04 has 3.14.3
  • Fedora 44 has 3.14.4
  • Buildroot has 3.14.5
  • Yocto has 3.14.5
• drawbacks:
  • Debian 13 Trixie only has 3.13.9 :-(

Tasks:

• strictly required:
  • update the projects requierments
  • fix new linter errors (e;g. black will find more issues in existing code)
  • where they exist, ensure tests still succeed; fix the code and/or the test appropriately
• nice to have:
  • update existing code to new features availqble with python 3.14

Contingency plan:

Apart from linter errors, there are no blocking issues identified that would prevent existing code to work with a newer Python version. If that proves to be wrong and an insurmontable issue arises, the contingency plan is thus relatively simple: do not merge the branch.

If issues are detected after the branch is merged, they shall be considered regressions and fixed. There will be no walking back after the merge.