[Zope] How to debug access denials?

[Stephane Bortzmeyer]

I have problem with Zope security model and I would like to know the
best way to debug Zope when access is denied. 

I have two experimental sites: on one of them, anonymous users can go
everywhere. On the other, the permissions *look* exactly the same but
anonymous users can only see the home page and are denied access to
subfolders (more precisely, Zope asks a password). I assume one DTML
method, in the second site, is doing something forbidden (anonymous
has "View" and "Access content information").

Is there a way to get an extended log, such as "anonymous user denied
because index_html called standard_html_header which called getData
and getData is a database connection and they don't have permission to
use database connections"?