What happened to Idle's extend.py?

[David Morgenthaler]

Idle-0.3, shipped with Python 1.5.2 had an extend.py module that was
used to extend Idle. We've used this extensively, building entire
"applications" as Idle extensions.

Now that we're moving to Python 2.1, we find the same old directions
for extending Idle (in extend.txt), but there appears to be no
extend.py in Idle-0.8.

Does anyone know how we can add extensions to Idle-0.8?

Thanks in advance,
David