Mod_python error: "PythonHandler mod_python.publisher"

Traceback (most recent call last):

  File "/usr/lib64/python2.4/site-packages/mod_python/apache.py", line 299, in HandlerDispatch
    result = object(req)

  File "/usr/lib64/python2.4/site-packages/mod_python/publisher.py", line 213, in handler
    published = publish_object(req, object)

  File "/usr/lib64/python2.4/site-packages/mod_python/publisher.py", line 412, in publish_object
    return publish_object(req,util.apply_fs_data(object, req.form, req=req))

  File "/usr/lib64/python2.4/site-packages/mod_python/util.py", line 439, in apply_fs_data
    return object(**args)

  File "/var/www/vhosts/visitflanders/htdocs/do/ecco.py", line 287, in cview
    (listid, listcatid, itemid) = EccoViewAction.lookup_codes(listcode, catcode, itemcode)

  File "/var/www/vhosts/visitflanders/htdocs/do/eccocms/EccoViewAction.py", line 332, in lookup_codes
    assert listid, "Non-existent list code specified! [%s]" % listcode

AssertionError: Non-existent list code specified! [index.htm]