Comment 1 for bug 429473

This can/should only happen in very limited circumstances. The error is probably happening in tales.py:585 right? If so it means that one of these conditions is true:

* You've set override_title_breadcrumbs=True on your view class
* No +hierarchy adapter could be found for your context+request
* The +hierarchy adapter was found but its .display_breadcrumbs property returned False

If one of these things is true, it basically means it can't use breadcrumbs, either because they aren't available or you've told it to override the breadcrumbs. In that case, it first looks for view.page_title attribute and uses that if available. If that's not available, it uses the first of view.template.filename and view.index.filename to calculate a file name for pagetitles.py. If it finds none of these, it returns the DEFAULT_LAUNCHPAD_TITLE. If however, it finds a filename attribute but cannot find an entry in pagetitles.py for this filename (s/-/_/ of course), then it raises an assertion.

Can you provide more information, specifically why is it not finding a +hierarchy adapter, or why it is not finding a page title under the above search rules? Some odd views don't fit into these rules and you'll get the assertion. (An example is TeamInvitationView in person.py).