Bug#706110: libgnome{, vfs}2-common: fails to upgrade from squeeze: prerm failure: gconf-schemas: not found

[Julien Cristau]

On Thu, Apr 25, 2013 at 14:09:24 +0200, Michael Biebl wrote:

> Am 25.04.2013 01:11, schrieb Michael Biebl:
> > According to jwilk, this is a issue in the python package:
> > <jwilk> mbiebl: I'm pretty sure it's not /usr/sbin/gconf-schemas that is
> > missing, but /usr/bin/python (which is is -schema's shebang).
> > <jwilk> Or more precisely, /usr/bin/python is there, but it's dangling.
> > <jwilk> I looked at the build log and yeah, this is what happend: python
> > is upgraded from 2.6 to 2.7, making /usr/bin/python dangling, because
> > python2.7 is not unpacked yet.
> > <jwilk> Then libgnome2-common is unpacked, which doesn't work without
> > working /usr/bin/python.
> > <jwilk> s/unpacked/prerm'ed/ in the last sentence.
> 
> Adding an empty prerm can be considered a hack at best. Given that we
> have 220+ packages which ship gconf schemas, adding it back to a single
> package would be an incomplete fix anyway.
> 
> dondelelcaro on #debian-devel suggested:
> 
> <mbiebl> dondelelcaro: as for pre-depends: where would you add that?
> <dondelelcaro> mbiebl: to python-minimal
> <dondelelcaro> mbiebl: because right now, the Depends doesn't take
> effect until python-minimal is configured, even when it is unpacked.
> <dondelelcaro> mbiebl: so that's why you have a dangling symlink
> <dondelelcaro> mbiebl: so if something that calls gconf-schema gets
> called after python-minimal is unpacked, but before python2.7 is, you
> get breakage.
> 
> jwilk suggested:
> <jwilk> Don't use Python (or anything non-essential) in maintainer
> scripts (except maybe postinst), ever.
> 
> Looking at /usr/bin/gconf-schemas, it's a rather simple python script.
> Re-implementing it in shell shouldn't be too hard.
> 
> release team, any opinions, preferences how to address this bug?
> 
Thoughts in random order...
1) this is terrible
2) in the absence of loops, dpkg ought to unpack python2.7-minimal
   before python-minimal
3) adding pre-depends at this stage makes me extremely wary
4) rewriting gconf-schemas only helps if gconf-schemas is upgraded
   before its reverse deps
5) do we know why this only shows up now, and if there are real world
   cases where this issue occurs?

Cheers,
Julien
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