Check for parent/mod as well as parent.mod in findext. Debian/Ubuntu ship a system-wide hgrc that loads extensions using the syntax hgext/extension=, rather than hgext.extension=. Although the extensions work correctly, hg help <extension> doesn't understand this form without this patch.

#header#
# HG changeset patch
# User #author#
# Date #date|hgdate#
# Node ID #node#
#parent%changesetparent#
#desc#

#diff#