I don't really use pydoc.el for anything myself nor do I know whether
its functionality is already included in newer python-mode.el's, but I
found that pydoc.el doesn't find pydoc_lisp.py out of the box, and
thought might as well fix it.
Test case: start XEmacs, do M-x pydoc-commands RET
Fix attached; Skip, let me know if you'd like me to commit this.