We were checking if an OperationalError was thrown when checking if a

diff dedup was needed during upgrade. Turns out, ProgrammingError can

also be thrown. We may find that more errors could be thrown in the

future.
We unit test that the unmigrated() function works, and Django's count()

should always work. So, trusting that, we're now just catching all

exceptions, instead of white-listing several exceptions. This will help

protect from new errors in the future (depending on database), and

ensure that the user will always be able to get through this (very

unimportant) part of the upgrade process.

Didn't do any testing, but this is pretty trivial.