It occurs to me on analysis of apt that the debsums part of this cannot
possibly cause an upgrade failure.  The reason for this is that DPkg
::Post-Invoke hooks are run in precisely three cases:

  1) waitpid for dpkg failed (i.e. some kind of programming error); return code 
from Post-Invoke is ignored
  2) dpkg exited with a non-zero wait status; return code from Post-Invoke is 
ignored
  3) every dpkg invocation in a complete apt run exited successfully

The mistake in my earlier analysis was that I believed that debsums
might be run in the middle of an otherwise successful apt run.  This is
not so, both from code inspection and empirically.  The only case in
which a non-zero exit code from debsums can make the slightest
difference to an upgrade is in case 3, and in that case it's running at
the end of a successful apt run so can reasonably assume that apt left
the perl packages in a sane state.  Even if it fails there, the worst
that happens is that it causes apt to exit non-zero after doing all its
work; it's not going to convert a complete successful run into a partial
failed run, which would be the real problem.

So, I think this is essentially cosmetic.  It showed up as a problem in
your original report because libwmf0.2-7's prerm had already failed,
upon which apt attempted to run debsums as part of general cleanup, but
it didn't actually make the situation any worse.  If the libwmf0.2-7
problem hadn't been present, you wouldn't have seen a problem with
debsums either.

I'll downgrade this to low and keep it open, because it might be worth
changing debsums to catch these errors and add a clarifying note that
it's probably due to Perl being mid-upgrade.  However, based on the
analysis above, I don't think we should muck around with debsums' exit
code.

** Changed in: debsums (Ubuntu Precise)
   Importance: High => Low

** Summary changed:

- perl-modules lucid->precise upgrade failure: debsums needs to restrict itself 
to Essential dependencies
+ perl-modules lucid->precise upgrade failure: debsums is noisy when 
Perl-related packages are inconsistent

** Tags removed: rls-mgr-p-tracking

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https://bugs.launchpad.net/bugs/901741

Title:
  perl-modules lucid->precise upgrade failure: debsums is noisy when
  Perl-related packages are inconsistent

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