If a strict umask in effect during cache file initialization,
apt-show-versions creates the files without read permissions for
If a non-root user runs apt-show-versions, this happens:
can't open /var/cache/apt-show-versions/ipackages: Permission denied at
/usr/bin/apt-show-versions line 213
Probably the easiest way to fix this would be to simply set umask to 022 at
the start of the program before calling Storable::store.