[PATCH] nmbug: explicitly prefer python3

[W. Trevor King]

On Sun, Feb 11, 2018 at 10:56:36PM -0500, Daniel Kahn Gillmor wrote:
> On Fri 2018-02-09 12:46:24 -0800, W. Trevor King wrote:
> > From later on in PEP 394 [1]:
> >
> >   It is anticipated that there will eventually come a time where
> >   the third party ecosystem surrounding Python 3 is sufficiently
> >   mature for this recommendation to be updated to suggest that the
> >   python symlink refer to python3 rather than python2.
> >
> > And from right up at the beginning [2]:
> >
> >   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.
> >
> > On my Gentoo system, I've also selected Python 3 to back ‘python’.
> > So I think your solution should be “add a /usr/bin/python symlink
> > to your python3”, not “claim that nmbug is only compatible with
> > Python 3”.
> 
> Presumably you still have /usr/bin/python3 in addition to
> /usr/bin/python as well.  So the one thing i think we're both
> agreeing on is that we use nmbug with python 3.

Yup.  But I'm not sure that is the case for all nmbug users.

> It looks to me like you're asking me to change my operating system
> to accomodate your naming preference.

No, I'm asking you to change your operating system to accommodate PEP
394's naming preferences.  As PEP 394 points out, Arch made the switch
to using ‘python’ for ‘python3’ long ago.  You'd just be following
their lead.

> I'm asking that we put the onus on developers who really insist on
> using nmbug with python 2.7 maintain their own local patch against
> nmbug, rather than other developers either modifying their local
> operating system in potentially disastrous ways (/usr/bin/python as
> python3 would cause severe breakage for at least one python2-only
> tool i rely on daily, sadly)…

That Python-2-only tool should be using python2 in its shebang.  This
is exactly the sort of issue that PEP 394 was created to address.
Once you patch that tool to follow PEP 394, you should have no problem
adjusting your system to also follow PEP 394.

> … or carrying their own local patch against nmbug.

A shebang with ‘python’ should work with everyone (and it's what PEP
394 recommends for scripts that work with both Python major versions).
The only folks who would need a local patch would be folks with
systems like your current plan that contain no ‘python’ command at
all.  I see no upside to such systems, while I do see upsides to
systems with just a ‘python2’ (and a ‘python’ alias for it) or just a
‘python3’ (and a ‘python’ alias for it).

> i'll drop this request now because i don't understand the origin of
> the strength of your reaction, and already wish i'd spent the time
> i've lost on it on something more productive :( I hope if you change
> your mind you'll come back and recommend it here.

I like nmbug and have put some time into it.  But I'm not the notmuch
maintainer, and as you point out, nmbug would still work for me with a
python3 shebang.  So if the maintainers want to switch to python3 it's
no skin off my back.  They can always wait and field requests from any
python2-only users if/when those users file complaints (which may be
never).

Cheers,
Trevor

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