[Zope-PTK] LoginManager wants PARENT_URL?

[Dan L. Pierson]

When I try to add a LoginManager (under 2.1.4 or CVS) I get a KeyError 
for PARENT_URL.  There is indeed a reference to REQUEST['PARENT_URL']
in LoginManager.py, but I can't find any place that this is set.
Grepping all of the CVS Zope sources doesn't find any other reference
to it and it doesn't seem to be documented anywhere.

No one else has complained about this so it must be something obvious
I've missed, will some kind person please enlighten me?

Dan Pierson