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

[Markus Armbruster <armbru@redhat.com>]

Stefan Hajnoczi <stefanha@gmail.com> writes:

> On Mon, Aug 21, 2017 at 04:29:44PM +0200, Markus Armbruster wrote:
>> What is our Python 2 -> 3 migration strategy?
>> 
>> Don't support Python 3 until a flag day, then flip and don't support
>> Python 2?
>
> Add support for Python 3 so that both Python 2.6+ and Python 3 are
> supported.

Python 2.7 is the end of the Python 2 line of development (PEP 404).
It'll be maintained until 2020.  Downstream support for Python 2 may or
may not last longer.

> When Python 2 is EOL it will need to be dropped and the code becomes
> Python 3-only.
>
>> Keep the source in Python 2 and support 3 via conversion with 2to3?
>> 
>> Port the source to Python 3 and support 2 via conversion with 3to2?
>> 
>> Port to Python 3, but keep it working with Python 2 with help of the six
>> module?
>> 
>> Support both with ad hoc hackery (like this patch does)?
>
> Yes, please see for details:
> https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg01758.html

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?