Bug#767554: python-persistent and python-zodb: error when trying to install together

[Arnaud Fontaine]

Hello,

Andreas Beckmann <anbe at debian.org> writes:

>  Package: python-persistent,python-zodb
>  Version: 4.0.8-1
>  Severity: serious
>  User: treinen at debian.org
>  Usertags: edos-file-overwrite
>  Control: found -1 1:3.9.7-2

First of all, thanks for finding and reporting such issues, it's greatly
appreciated!

>   Selecting previously unselected package python-zodb.
>   Preparing to unpack .../python-zodb_1%3a3.9.7-2_amd64.deb ...
>   Unpacking python-zodb (1:3.9.7-2) ...
>   dpkg: error processing archive /var/cache/apt/archives/python-zodb_1%3a3.9.7-2_amd64.deb (--unpack):
>    trying to overwrite '/usr/lib/python2.7/dist-packages/persistent/wref.py', which is also in package python-persistent 4.0.8-1
>   Errors were encountered while processing:
>    /var/cache/apt/archives/python-zodb_1%3a3.9.7-2_amd64.deb
>
> This is a serious bug as it makes installation fail, and violates
> sections 7.6.1 and 10.1 of the policy. An optimal solution would
> consist in only one of the packages installing that file, and renaming
> or removing the file in the other package. Depending on the
> circumstances you might also consider Replace relations or file
> diversions. If the conflicting situation cannot be resolved then, as a
> last resort, the two packages have to declare a mutual
> Conflict. Please take into account that Replaces, Conflicts and
> diversions should only be used when packages provide different
> implementations for the same functionality.
>
> Here is a list of files that are known to be shared by both packages
> (according to the Contents file for sid/amd64, which may be
> slightly out of sync):
>
>   usr/lib/python2.7/dist-packages/persistent/__init__.py
>   [...]

From upstream point  of view, ZODB3 (aka python-zodb in  Debian) used to
include persistent, BTrees,  ZODB and ZEO modules.  However, since ZODB3
3.11.0a1, upstream  has split it  up into  4 distinct packages  (one for
each module),  bump the version  to 4.0  and made ZODB3  a "metapackage"
depending on all of them.

As of  fixing this RC  bug for Jessie:  Among the four,  only persistent
package is currently available in Debian, so  there is no way to get rid
of  ZODB3 (at  least for  Jessie). Barry:  If persistent  >= 4.0  Debian
package is useful on  its own to anyone (and thus  should not be removed
From testing),  then can I  add a Conflict  on both packages  and upload
them to fix this bug?

Cheers,
-- 
Arnaud Fontaine
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