add DEPRECATION grace period: the upcoming Great Python2 Purge™

[Pjotr Prins]

On Wed, Dec 26, 2018 at 01:30:53PM +0100, Marius Bakke wrote:
> Efraim Flashner <address@hidden> writes:
> 
> > We're now about a year out from the official EOL for python2 (Jan 1,
> > 2020). So far we've been not adding python2 variants of packages that
> > are new unless they're actually needed for something. Do we want to
> > start removing python2 packages when updating other packages if they are
> > leaf packages?
> 
> I think it's okay to start removing "leaf" Python 2 packages.  In most
> cases they were probably never used anyway, or the dependents have
> transitioned to their Python 3 counterparts.
> 
> We'll probably break some channels, but I'm sure our users won't have
> any difficulties adding them back to their own channels if need be.
> 
> On a related note, we also have a number of [Python 3] packages that
> have been failing to build for a long time.  Some of these are trivial,
> i.e. what "guix import" produces.
> 
> It would be good to get rid of those as well, as the would-be user is
> much better off starting from "guix import" instead of first getting
> disappointed by the Guix package and then having to go through all the
> trouble of submitting a patch.
> 
> Should we have some sort of policy or threshold for when to remove such
> packages?  Maybe after 3-6 months?

A lot of software outside Guix still depends on Python2, for better or
worse. I don't believe EOL means they are going to drop security
updates. Leaf packages may well be in use today.

Is there a way we mark packages as DEPRECATED? I think we should not
just remove packages without a grace period. Deprecate for, say, 3
months or even 6 months is the way to do this. A deprecation tag
should include a time stamp that gives the (planned) removal time.

Pj.