[testlib] we should not replace db-name in sources, this cause undesired side effect (when running pytest on whole cw for instance). Proper fix in logilab.database

[web] put a fake object that raise Unauthorized on any attribute access as req.cnx and req._user, so we are properly asked to authenticated on any view that tries to do something with one of those attributes (instead of doing defensive programming everywhere we're doing that)