Debugging Unauthorized and turn off redirect
Today I had to debug a security related problem. In a complex site at some places a Unauthorized came up. I did all the holy steps needed I know (see plone.org/documentation/kb/debug-unauthorized). It still ate up my error-message and even with log level DEBUG at all places no output with any value was available. This primary because the redirect to the login_form happened.
Ok, where can one turn off redirect to the login_form? To find this I had to step through the publishing process and found one of these lovely monkey-patches of Plone. It patches quiet and hidden and so it took me a while to recognize:
It is in plone.app.linkintegrity. The patch code itself is in monkey.py while patching happens in the __init__.py on zopes inititialize call.
I commented the line with monkey.installExceptionHook() and afterwards I got a wonderful traceback in my error_log.
I hope this may help somebody else.