Python 3.5 as a system-wide change for Fedora 23?

[Matej Stuchlik]

Hey Nick,
sorry for the late response, I wanted to talk this through with the
rest of the Python Maintainers to get their input as well. :)

----- Original Message -----
> From: "Nick Coghlan" <ncoghlan at gmail.com>
> To: "Fedora Python SIG" <python-devel at lists.fedoraproject.org>
> Sent: Monday, June 15, 2015 2:49:45 AM
> Subject: Python 3.5 as a system-wide change for Fedora 23?
> 
> Hi folks,
> 
> Toshio pinged me about a problem with dnf using -OO in their shebang
> lines earlier today
> (https://bugzilla.redhat.com/show_bug.cgi?id=1230820), which got me
> thinking about our Python 3.5 adoption timeline (as I note in the
> issue there, the reason using -OO in system packages is currently a
> bad idea is a limitation in CPython's bytecode caching scheme that
> Brett Cannon has fixed for 3.5+).
> 
> The two relevant schedule docs are the ones for F23 and Python 3.5:
> 
> Fedora 23: https://fedoraproject.org/wiki/Releases/23/Schedule
> Python 3.5: https://www.python.org/dev/peps/pep-0478/
> 
> The upstream Python 3.5rc1 release is due on August 9, while the final
> release is due on September 13. To switch in F23 that would mean:
> 
> * getting a system-wide change for a Python 3 upgrade approved by the
> F23 deadline on Jun 26
> * getting a 3.5 beta release incorporated by the testability deadline
> on July 28 (this would likely correspond to 3.5b3 upstream, which is
> due for release on July 5)
> * F23 Alpha would ship with a Python 3.5 beta release
> * F23 Beta would ship with a Python 3.5 release candidate
> * F23 final would ship with the Python 3.5.0 final release

We feel that that's perhaps a little tight schedule, where things could
go wrong easily. For that reason we'd like stay with Python 3.4 as system
python for Fedora 23, while providing Python 3.5 in a Copr. (Perhaps using
Miro's repo)

Does that make sense?

In any case, thank you for taking the time to write this, the Beaker
note bellow is sure to be useful eventually. :)

Matt

> Slavek's change proposal for the 3.4 upgrade in F21 is at
> https://fedoraproject.org/wiki/Changes/Python_3.4
> 
> Progress on the "Python 3 as default" effort means that the Py3 stack
> is significantly more critical now than it was back then. However, we
> also have better testing tools available.
> 
> In particular, for testing purposes prior to making the change in
> Koji, I'd suggest we consider Beaker's /distribution/rebuild task:
> https://beaker-project.org/docs/user-guide/beaker-provided-tasks.html#distribution-rebuild
> 
> The example given there is for testing GCC changes, but it should work
> for this as well (while beaker.fedoraproject.org isn't open for more
> general access yet, I still have an account there from when I was
> working on the Beaker team, and worst case, we can do the test on Red
> Hat's Beaker internal instance instead).
> 
> The contingency plan if the Beaker rebuild showed significant problems
> that couldn't be resolved by the testability deadline would be to
> postpone the system-wide change to Fedora 24 (however, I'd consider
> issues of that magnitude to indicate an upstream compatibility
> problem, so it hopefully won't come to that)
> 
> If folks think this sounds like a plausible approach, I'd volunteer to
> work with Matej as Python 3 maintainer to push it forward.
> 
> Regards,
> Nick.
> 
> P.S. Miro's nightly SCLs at
> https://copr.fedoraproject.org/coprs/churchyard/python3-nightly/ may
> also have a part to play, although I'm not sure what that would be
> just yet
> 
> --
> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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