How the hell do I debug assert _context.stack[-1].context is context

Hi guys,

We're diving into Z3/Five very seriously for the future Plone 3.0 release,  
and mostly it's proving a great benefit. However, I have one recurring  
problem (that I'm sure I'm not alone about).

Products/CMFPlone/configure.zcml includes an <include package=".browser"  
/>. This in turn has an <include package=".contentmenu" /> (not in svn  
yet, but you get the idea - I doubt the second include makes any  
difference anyway).

This file references interfaces (for=".interfaces.IFooBar"), classes  
(class=".menu.ActionsMenu") etc. If there are any errors in that file - if  
I refer to an interface that doesn't exist, for example, or if there are  
syntax errors or run-time errors reading in the modules .interfaces or  
.menu, I get this:

  LOG('Five', ERROR, 'Could not import Product %s' % product.__name__,  
error=exc)
Traceback (most recent call last):
  File "testMenu.py", line 9, in ?
    from Products.CMFPlone.tests import PloneTestCase
  File  
"/Users/optilude/Development/Plone/Personal/plone3.0-zope2.9/Products/CMFPlone/tests/PloneTestCase.py",  
line 7, in ?
    from Products.PloneTestCase.ptc import *
  File  
"/Users/optilude/Development/Plone/Personal/plone3.0-zope2.9/Products/PloneTestCase/ptc.py",  
line 16, in ?
    from Products.PloneTestCase.setup import PLONE21
  File  
"/Users/optilude/Development/Plone/Personal/plone3.0-zope2.9/Products/PloneTestCase/setup.py",  
line 54, in ?
    ZopeTestCase.installProduct('Five')
  File  
"/Users/optilude/Development/Plone/Zope/2.9/current/lib/python/Testing/ZopeTestCase/ZopeLite.py",  
line 157, in installProduct
    get_folder_permissions(), raise_exc=1)
  File  
"/Users/optilude/Development/Plone/Zope/2.9/2.9.2/lib/python/OFS/Application.py",  
line 790, in install_product
    initmethod(context)
  File  
"/Users/optilude/Development/Plone/Zope/2.9/2.9.2/lib/python/Products/Five/__init__.py",  
line 29, in initialize
    zcml.load_site()
  File  
"/Users/optilude/Development/Plone/Zope/2.9/2.9.2/lib/python/Products/Five/zcml.py",  
line 41, in load_site
    _context = xmlconfig.file(file)
  File  
"/Users/optilude/Development/Plone/Zope/2.9/current/lib/python/zope/configuration/xmlconfig.py",  
line 554, in file
    include(context, name, package)
  File  
"/Users/optilude/Development/Plone/Zope/2.9/current/lib/python/zope/configuration/xmlconfig.py",  
line 492, in include
    assert _context.stack[-1].context is context
AssertionError

It must swallow an exception somewhere, but I can't figure out where. The  
code is confusing to me, and my attempts at pdb didn't get me any closer.

I'm wondering if I'm doing something wrong - in which case, please let me  
know. I've lost probably a few hours to this thing over the past week,  
because things that are very simple become nearly impossible to locate  
without significant amounts of trial-and-error. :-(

Martin

--
"You can just adapt yourself out of it..." // Archipelago sprint 26/04/2006