[Import-SIG] PEP 420 issue: extend_path

["Martin v. Löwis"]

I'd like to propose that pkgutil.extend_path is specified to also 
consider portions according to the PEP. Currently, it will only
consider portions having an __init__.py

If a namespace package gets a portion installed that has an __init__.py, 
then all existing portions become ignored under
the current PEP. With that change, if a portion has an __init__.py
that uses extend_path, the other portions would still be considered.

With the current PEP, all contributors to a package need to 
simultaneously agree to drop their __init__.py for 3.3. Initially,
this could cause confusion, and hinder adoption of the PEP.

The same would also apply to pkg_resources.declare_namespace.
Unfortunately, this is out of the scope of the PEP, but I'm sure Tarek
would accept a patch to distribute to bring it into conformance to
pkgutil.

Interestingly, it appears that pkg_util will break under PEP 420, 
anyway, as it currently does (in _handle_ns)

     loader = importer.find_module(packageName)
     if loader is None:
         return None
...
         loader.load_module(packageName); module.__path__ = path

Now, if loader suddenly becomes a string, than the load_module
call will raise an attribute error (untested).

Regards,
Martin