Bug#180227: prebaseconfig: 90prepare-base-config fail on CD installs

[Petter Reinholdtsen <pere@hungry.com>]

Package: prebaseconfig
Version: 0.022
Severity: important

The fix for bug #148606 breaks CDROM installs.  The script
90prepare-base-config checks for /cdrom/.disk/base_installable after
the CD is umounted (done by 15cdrom-detect), and when the file is
missing tries to look up network specific debconf variables.  These
are missing, and the script terminates.

I suggest moving the code somewhere else, and perhaps adding another
debconf variable for the suite, instead of using the same variable to
store both stable/testing/unstable and woody/sarge/sid.