File paths containing ':' messes up loader
method "isPath" of BaseLoader raised an Exception:
TypeError: object of type 'NoneType' has no len()
The key factor to trigger the bug is having character ":" in an url that should be checked through 'isPath' method.
You should be able to check this by renaming your zope application path to add a ":" character in it.
I have joined a simple fix.