Debian says "Warning! you are running an untested version of Python." on 2.3

[Alex Stapleton]

Whenever I run python I get

"Warning! you are running an untested version of Python."

prepended to the start of any output on stdout.

This is with Debian and python 2.3 (running the debian 2.1 and 2.2 binaries
doesn't have this effect)

Does anyone have any idea how to stop this or have even seen it before?
Google says Your search - "you are running an untested version" - did not
match any documents
:(