Re: [Qemu-devel] Deprecation policy and build dependencies

[John Snow]

On 6/4/19 1:31 AM, Markus Armbruster wrote:
> Peter Maydell <address@hidden> writes:
> 
>> On Mon, 3 Jun 2019 at 19:21, John Snow <address@hidden> wrote:
>>> I get it, we don't want to require Python 3.8 because some dev wanted
>>> assignment conditionals -- but we're talking about Python 2 here, which
>>> suffers its EOL by the end of this calendar year.
> 
> "Not because some dev wanted assignment conditionals" is the non-reason.
> Let me spell out the reason: supporting Python 2 is expensive for us.
> As the amount of Python code grows, it gets more and more expensive.
> 
> Is this really time and effort well spent?
> 

I'd just like to clarify that you and I are arguing the same point. I
used that non-reason intentionally, arguing that we don't want a trivial
feature, we're talking about the major deprecation of an entire version
of a language.

I picked a far-fetched, very bleeding edge version (and a feature in it
that matched, sorry, been doing a lot of Python lately) to counter
Peter's point that we didn't want to support bleeding-edge stuff "just
because."

Sorry if I didn't articulate this point well.

>>> So do we think it's reasonable to drop support for Python2 for the
>>> release that comes out after Python2's EOL, or do we insist on 2x3
>>> simultaneous support for years more?
>>
>> I don't have a strong opinion on Python in particular, but
>> I think it would be nicer to avoid the "python is a special
>> snowflake" effect.
> 
> Lots of things are nice.  Limited resources dictate we can only get some
> of them.
> 
>>                    Would it really be so bad for it to just
>> be "drop it when it falls off the last LTS distro" like the
>> rest of our dependencies ?
> 
> In my experience maintaining and evolving the QAPI generators,
> supporting both Python 2 and 3 is a constant distraction that adds up
> over time.  It's all manual; we decided against adopting one of tool
> chains made for dealing with this mess.  I'd rather think about how to
> solve real user problems like deprecation information or command line
> introspection than deal with Python 2 vs. 3 arcana.
> 
> Just the other day, I flagged an innocent-looking simplification of some
> non-QAPI Python code that changed semantics subtly on Python 2, impact
> unknown.  The developer did not know.  The fact that I waste precious
> brain capacity on knowing this shit (pardon my French) is a bloody
> shame.  Well, some of this shit, because I've screwed it up myself, too.
> 
> The sooner we stop the bleeding, the better.
> 

I agree, and it looks like we have consensus that because RHEL7 has
EPEL, we can drop Python 2 support. I think.

What wasn't made clear to me yet is in which version we may do so. I
think I suggested 4.2, and nobody agreed or disagreed with that point.

--js