Better handle and document Python needs for Kernel build

Hi Jon,

It follows the second version of this small series. It contains missing patches from the python backward-compatibility series.

I dropped support for 2.7 and did some changes at changes.rst per Akira's request.

They're not urgent, IMO it should be OK to have them merged for 6.17.

The first patch ensures that kernel-doc won't crash with version 3.2 (tested on 3.4, as 3.2 is like an unicorn: docker containers v1 don't run anymore on Fedora, building is broken since at least Fedora 32, Anaconda doesn't have it anymore).

With this change, on elder versions, it would emit a warning and do nothing, as the actual code depends on features at 3.6 (f-strings) and 3.7 (ordered dict).

The second patch changes process/changes.rst. Currently, it makes one think that Python is optional. While not having python may work on some cases, it breaks on arm/arm64 with defconfigs. It also breaks with allyesconfig/almodconfig (at least on x86/x86_64), with clang (on some archs) and apparently on some other subsystems that I didn't care enough to identify, as for me, breaking on arm/arm64 with defconfigs, and on x86/x86_64 with allyesconfig/allmodconfig is enough evidence that this is mandatory nowadays.

So, remove optional from Python and add a quick description about where it is required, leaving it open to one's imagination that it could break with other configs we didn't map.

---
v2: drop support for 2.7, updated a comment and updated changes.rst.

Mauro Carvalho Chehab (2):
docs: kernel-doc: avoid script crash on ancient Python
docs: changes: better document Python needs

 Documentation/process/changes.rst |  9 +++++++-
 scripts/kernel-doc.py             | 34 ++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 11 deletions(-)

2.49.0