Package: libsane1
Version:

When upgrading from Daedalus to Excalibur, the usrmerge configure step fails on following files provided by libsane1 package:

/usr/lib/udev/hwdb.d/20-sane.hwdb
/usr/lib/udev/rules.d/60-libsane1.rules
/usr/lib/udev/rules.d/99-libsane1.rules

When this happens in su/sudo environment, the user can not escalate priviledges anymore because packages providing PAM authentication are not correctly upgraded yet.

Hotfix: Reboot to recovery console and delete mentioned files manually, then:
# apt-get install -f
# apt-get dist-upgrade
and reboot.

Circumvention: Execute "apt-get dist-upgrade" from root shell.