[Catalog-sig] PEP 345 Update

[P.J. Eby]

At 10:40 AM 8/24/2010 -0400, Fred Drake wrote:
>On Mon, Aug 23, 2010 at 7:05 PM, P.J. Eby <pje at telecommunity.com> wrote:
> > Hm.  Come to think of it, if all Conflicts is saying is, "I have modules of
> > the same names as...", then couldn't any installer worth its salt figure
> > this out for itself?  (Even PEP 376 already has a way to detect conflicting
> > files before installing.)
>
>This is not the only case that's interesting for Conflicts.  Certain
>refactoring patterns can cause incompatibilities as well, and those
>can be much harder to track down.
>
>A new package which provides an interface that was once provided
>elsewhere should generally be declared in conflict with older versions
>of the package where the interface was originally provided (though not
>in conflict with newer versions that pull the interface from the new
>package).
>
>This pattern has occurred frequently as the Zope community has worked
>to reduce the dependencies on the zope.app packages, and there's been
>no way to declare the conflicts.

Could you give a concrete example of this?  I *think* I get the gist 
of what you're saying, but I'm not sure.