[LyX/ next] Prepare the removal of Python 2 support

[Pavel Sanda]

On Fri, May 31, 2024 at 12:19:53PM +0100, José Matos wrote:
> It is important to distinguish in this conversation two aspects of LTS:
> 
> * servers;
> * desktop computers.
> 
> Or else with the last round of supports we will feel bounded to support
> +15 year distributions. :-(

Right, we don't have to be religious about the LTS deadlines and I was not
pushing it for 15y old servers. In my experience though I still see actively
used systems based on rhel 8 / ubuntu 20 around so the plan to cut them now
seems premature even when considering >2y of our release cycle. 

> Another important distinction to make here is in these arguments are if
> the issues are related to the users or to the developers?
> 
> Because sometimes in the conversations they are mixed and they clearly
> correspond to different concerns.
> 
> For developers the releases correspond to what exists now, while for
> users the concern are the distributions that will be available when the
> first stable version is released.

We can distinct these two, but my conclusion would be the same for both.

> > Anyway, my breakdown would be:
> > 
> > LyX 2.4 requires GCC 4.9, Python 2.7/3.5, Qt 5.4 (>=5.6 suggested)
> > 
> > This is what I see wrt ubuntu:
> > focal/20.04 (sec support till 2030): GCC 9.3, Qt 5.12, Python 3.8.2
> > Older do not ship python 3 / Qt 5, end of story.
> > 
> > Redhat world:
> > RHEL 7 is dead, Searching RHEL 8 (sec support till 2029) packages
> > seems behind redhats login wall but when I look on pkgs.org (sorry if
> > I mess up, not expert in redhats ecosystem) I see GCC 8.5, Qt 5.15, I
> > don't see python3 packages, but when login on nearby rocky 8.9
> > machine I see:
> > $ python3 --version
> > Python 3.6.8
> > 
> > 
> > The lower intersection gives GCC 8.5, Qt 5.12, Python 3.6, if, as you
> > say, is easy to update python3 in rhel, maybe 3.8 then.
> 
> I can work with 3.8 with the walrus operator, that is also quite
> helpful for our code:
> https://docs.python.org/3/whatsnew/3.8.html#assignment-expressions
> 
> One advantage of 3.9 for our code is the support of Type Hinting
> Generics in Standard Collections:
> https://docs.python.org/3/whatsnew/3.9.html#type-hinting-generics-in-standard-collections
> 
> This will help us to better document our code and to advantage of
> static analysis to find problems.

If you maintain that it's easy for on rhel 8 system to upgrade / run in parallel 
python >= 3.8 we could perhaps bump to 3.8.

Pavel
(For me personally even 3.9 works, but beyond that the discussion might become less civil :)