Useful when you have permission problem on which permission policykit handles. (network disk mounting power management ...)

If your problem seems related to debconf database corruption, be it of
above kind or not, the suggested fix is, quoting Joey Hess message in
#198297 bug page

By purging and reinstalling the package, you only fixed the entries for
that package. I suggest you run /usr/share/debconf/fix_db.pl as root,
which will delete all the orphaned questions. You may end up having to
repeat your answers to some debconf questions during future upgrades,
but that's a small price to pay for a consistent debconf database.

After running /usr/share/debconf/fix_db.pl as root, please look which
templates were affected,

$ diff -u /var/cache/debconf/config.dat{-old,} | grep ^[+-]Name
$ diff -u /var/cache/debconf/templates.dat{-old,} | grep ^[+-]Name

Your debconf database should be now in a consistent state and packages
configuration should succeed.