Filing Bugs for Python 3 Switch

[Bohuslav Kabrda]

----- Original Message -----
> On Thu, 29 Jan 2015 09:39:28 -0500 (EST)
> Bohuslav Kabrda <bkabrda at redhat.com> wrote:
> 
> > Not sure about it being the default, but we've been testing it in
> > DevAssistant for dependency installation on Python 3 and never
> > encountered any problems. I was also contacted by dnf maintainer with
> > a question on how to switch "dnf" to use
> > "python3-dnf" (package-wise), so I guess that's what will be done for
> > F22 (but that's just my guess, dnf maintainer would have to comment
> > here).
> 
> See the thing there that makes my teeth itch is: dnf has been
> massively great about having a long on-ramp. It appeared, it didn't
> replace yum, it let people try it out and report bugs, there was a long
> time of testing. Thats all great. But now, we switch it to dnf-3 and...
> that has not had years of running in rawhide and other releases, it has
> not had people testing it and reporting bugs. While the code overlap
> could be pretty large, I am willing to bet a shiny us dollar that there
> are some python 3 specific bugs lurking in it.
> 
> So, we turn on this not very tested path and immediately try and use it
> as default in anaconda and a new release. What happened to our nice
> long ramp? Or any ramp?

I just had a quick IRC chat with DNF maintainer and he said we still wants to switch to py3 for F22.

> > > Even still, that hinges on DNF being the default package manager in
> > > F22.  There are some concerns that it won't make it due to rel-eng
> > > tooling used to compose the images, etc.  If that's the case, yum
> > > will still be required.
> > 
> > Required, yes, but we'll still have tons of packages built with
> > Python 2. I never said that porting rel-eng tooling is the goal for
> > F22.
> 
> Might be good to note that on the change page:
> 
> We will not be replacing python2 entirely, it and packages that depend
> on it will still be available for now.

Doesn't [1] say it?

> > So if more minimal is minimal buildroot, then we can achieve that,
> > since it only has python-libs because of gdb and gdb can be rebuilt
> > with Python 3 (upstream source is compatible). If that means minimal
> > cloud image, then we can do it (we're waiting for the cloud-init
> > folks to accept the py3 patches, which should happen any time now).
> > If that means content from fedora-live-base.ks, then we can do pretty
> > much everything, except of samba (I think) - and Petr Viktorin is
> > doing some talking to people to get rid of samba from this config,
> > because it seems to be unnecessary there.
> 
> ok. So, perhaps we should have a change around this for f22, but it
> should be: Python 3 migration improvements or something, not
> 'default' ?

Yeah, as noted by Stephen Smoogen, I think the problem is communication here. Judging from reactions of people who I talked to, everyone takes it as "FESCo thinks that Python 3 is not ready and not the way to go right now". That's also what I thought when I read simple "defer this to F23". After these conversations here I'm starting to understand that this is not a message that FESCo meant to send. "Python 3 migration improvements" sounds about right to me and seems to send a better message than just deferring to F23.
Can someone from FESCo comment on this? If this sounds ok, shall I create a change page for it?

> > Considering all the information mentioned above and assuming Anaconda
> > makes it, I'd say it should be perfectly possible to declare Python 3
> > the default. As for the packages that are not in the minimal
> > installs, I can always open bugs for them before beta and only those
> > maintainers who believe it to be safe can switch.
> 
> Yeah, so if anaconda switches we get:
> 
> * anaconda switches to dnf (this is already done in rawhide after last
>   branch point, so I think it's quite safe/doable).
> * anconda switches to dnf-3 (if we land that change. It's gotten 0
>   testing that I know of).

As I noted above, DevAssistant devels have been using python3-dnf for quite some time now without any issues. I've written couple of scripts using python3-dnf and run them regularly without any issue. I even replaced "#!/usr/bin/python" by "!#/usr/bin/python3" in /usr/bin/dnf some time ago and everything still works (how ugly is that? :)). I know, that's not extensive testing, but it's certainly not zero.

> * anconda switches to python3 (it's almost ready, but no telling what
>   issues we will hit, it's not even landed yet).
> 
> Should we toss in a UI redesign so we can have Fedora 18 again?
> (sorry, that was rude of me)

Why not :)

> Wouldn't it be safer to defer dnf-3 and anaconda-py3 for next cycle,
> but make those changes in rawhide after the branch point? Then they
> would actually get months of shake out...
> 
> kevin

I'd say we should leave this up to developers of DNF and Anaconda. They're the best ones to say whether they're ready or not.

Slavek

[1] http://fedoraproject.org/wiki/Changes/Python_3_as_Default#Upgrade.2Fcompatibility_impact