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Excerpts from Gregory Haynes's message of 2015-12-09 12:49:07 -0800:
> Excerpts from Ian Wienand's message of 2015-12-09 09:35:15 +0000:
> > On 12/09/2015 07:15 AM, Gregory Haynes wrote:
> > > We ran in to a couple issues adding Fedora 23 support to
> > > diskimage-builder caused by python2 not being installed by default.
> > > This can be solved pretty easily by installing python2, but given that
> > > this is eventually where all our supported distros will end up I would
> > > like to find a better long term solution (one that allows us to make
> > > images which have the same python installed that the distro ships by
> > > default).
> > 
> > So I wonder if we're maybe hitting premature optimisation with this
> 
> That's a fair point. My thinking is that this is a thing we are hitting
> now, and if we do not fix this then we are going to end up adding a
> python2 dependency everywhere. This isn't the worst thing, but if we end
> up wanting to remove that later it will be a backwards incompat issue.
> So IMO if it's easy enough to get correct now it would be awesome to do
> rather than ripping python2 out from underneath users at a later date.
> 

+1 to spending a few brain cycles trying to decide if we can avoid churn
for users later. What we do in the guest should be carefully considered.

> > 
> > > We use +x and a #! to specify a python
> > > interpreter, but this needs to be python3 on distros which do not ship a
> > > python2, and python elsewhere.
> > 
> > > Create a symlink in the chroot from /usr/local/bin/dib-python to
> > > whatever the apropriate python executable is for that distro.
> > 
> > This is a problem for anyone wanting to ship a script that "just
> > works" across platforms.  I found a similar discussion about a python
> > launcher at [1] which covers most points and is more or less what
> > is described above.
> > 
> > I feel like contribution to some sort of global effort in this regard
> > might be the best way forward, and then ensure dib uses it.
> > 
> > -i
> > 
> > [1] https://mail.python.org/pipermail/linux-sig/2015-October/000000.html
> > 
> 
> My experience has been that this is something the python community
> doesn't necessarially want (it would be pretty trivial to fix with a
> python2or3 runner). I half expected some feedback of "please don't do
> that, treat python2 and 3 as separate languages", which was a big reason
> for this post. This is even more complicated by it being a
> distro-specific issue (some distros do ship a /usr/bin/python which
> points to either 2 or 3, depending on what is available). Basically,
> yes, it would be great for the larger python community to solve this but
> I am not hopeful of that actually happening.
>

Really there are 3 languages:

python2 only
python3 only
python2or3

And when you've been good and used python2or3 ... it would be nice to be
able to just express that without the machinery of setuptools and entry
points (which is the other option here btw)