[Rivet] Rivet release plan

[Frank Siegert]

Hi Andy, all,

> Given the embarrassing issue with the abspid() function that wasn't abs,
> as well as the CMS fixes, another CMS analysis to add, a fix to some
> HepData-produced ref data, and a few other tweaks... I think it's about
> time to release another Rivet update, 2.1.2. I'll try to get the
> necessary things done for that in the next week.

I've played around a bit with Rivet/YODA and Python3 last week (due to
an updated OS installation). It was a bit of a struggle to get it
working, and I'm not 100% finished yet (e.g. with some of the scripts
like yodamerge), but at least the build system and pyext stuff seems
to be working.

What are our Python3 compatibility plans... as early as possible in a
bugfix release, or rather aiming for the next larger release (e.g.
2.2.0) to make that available? I think some of the changes need to be
tested well on different systems and need more Python2/3 compatibility
wrapping than I have put in for my testing so far.

As a short term measure, I wonder whether we should follow PEP 394
(http://legacy.python.org/dev/peps/pep-0394/) and simply call python2
explicitly in all scripts:

  "- however, end users should be aware that python refers to python3
on at least Arch Linux (that change is what prompted the creation of
this PEP), so python should be used in the shebang line only for
scripts that are source compatible with both Python 2 and 3
- in preparation for an eventual change in the default version of
Python, Python 2 only scripts should either be updated to be source
compatible with Python 3 or else to use python2 in the shebang line."

I have checked that python2 is actually available in SLC5 and SLC6,
but I don't know whether we find any platform where that's not the
case (OS X?).

> Lastly, I'll just mention that we will have a new postdoc starting in
> Glasgow in August, a substantial part of whose time will be working on
> Rivet. So maybe we can organise a "sprint" shortly after he arrives.
> Having one before that would also be good, though... anyone want to host?

If you don't mind the suboptimal flight options, I'd offer to host one
of the next ones in Dresden, but only after October, as I might even
have some money then to cover at least some of the local costs.
As for one in/around August, I'm not available July 26 - Aug 6/9 (if
we happen to do it in Kopenhagen/Lund(?), Aug 6-8 would work great for
me, as I have to be in that area anyway around that time). After that,
and especially also in September, it looks quite good.

Cheers,
Frank