How to handle linked packages one of which is likely to cause breakage?

[jpenny@universal-fasteners.com]

I have recently become a maintainer.  I have volunteered with upstream to
become package manager, but not yet ITA'd PoPy and ZPopyDA.  I can package 
these, they are small easy to package programs.

But, here is the problem.  PoPy is a database adapter that allows
access to PostgreSQL.  As such, it has value  independent of 
ZPoPyDA , and has been packaged separately in the past.  ZPoPyDA 
uses PoPy to permit the Zope Database Adapter
technology to access PostgreSQL from inside Zope.

Recently upstream moved to release 1.x of ZPoPyDA.  This did two
things which will cause breakage for Zope users.  First, it made
a technolgy change that reduced the number of adapters needed
for most people.  This will not cause breakage, but people should
revise their applications to reduce the number of file descriptors open.

More importantly, the representation of booleans was changed from
T/F to 1/0.  This affects all logical statements against a boolean
retrieved from the database, and probably cannot be automatically
updated.

Questions:  1)  How do I alert adminstrators to the problem in such a
way that they are notified before any binaries are overwritten?

2)  ZPoPyDA and PoPy are version-linked, i.e. a particular version
of ZPoPyDA will typically only run agains a single version of PoPy.
Thus, ideally, I would like to prevent a system that has both
packages on it from completing the upgrade process until the
administrator launches a script to indicate readiness, while allowing
PoPy only systems to be upgraded without special intervention.
Is this possible?  How?

Thanks

Jim Penny