Some guesswork on my part...
Since python-2.3 resides in /usr/local it has very probably not been installed
with dpkg (or apt, for that matter), because no distro *ever* touches that
directory (or should burn in hell). So dpkg knows nothing about v2.3, only about
the other versions in /usr/bin.

Should the above be correct you might try obtaining the sources for cpia-control
and compile and install from there (probably to /usr/local as well, which would
be apropriate for *locally* compiled software.