Re: [Qemu-devel] [PATCH] scripts: Support building with Python 3

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On 31 August 2017 at 07:35, Markus Armbruster <address@hidden> wrote:
>> So, first we'll invest in work-arounds to make both 2 and 3 work.  Once
>> 2 is gone, we can invest some more to clean them up.  Which probably
>> won't happen, so we'll continue to carry work-arounds that no longer
>> make sense.
>>
>> I maintain roughly one fourth of all Python code in qemu, and I'm not
>> looking forward to this hoop-jumping at all.
>>
>> Are we really, really sure we want to go this way?  What exactly are we
>> hoping to accomplish by it?
>
> My take is that we have the following goals we want to achieve:
>
> (1) We need to continue to build and run on older (long-term-support)
> distros that still ship only Python 2.x (alas even back to 2.6)

That's an assertion, not an answer to my question :)

What exactly are we hoping to accomplish by supporting what distros
exactly?

> (2) We need to be able to build and run on newer distros that
> have dropped Python 2 altogether in favour of Python 3
> (I don't know if there are any such today, but presumably by
> 2020 there will be)

Yup.

> Unless we can confidently say that either (1) or (2) is the
> empty set, we need to handle both 2 and 3 in the same codebase.
> This is a pain, but unfortunately Python upstream have forced
> us into it by breaking source code compatibility.
>
> I think (1) is pretty clearly not (yet) an empty set, so the
> only alternative I see to "support 2 and 3 now" is "keep supporting
> only 2 for the moment and hope that no distro drops 2 support
> before all the LTS 2-only distro versions vanish into history".

I don't buy the "clearly" in "pretty clearly not (yet) an empty set",
because I don't understand *why* we need to support "older
(long-term-support) distros".

If we can leave Python 2 behind, I'm all for porting to Python 3 now.

If we can't yet, then I don't see why I should do work *now* just
because "some" distro might drop support for Python 2 "before all the
LTS 2-only distro versions vanish into history".

If it ain't broke, don't fix it!