[Zope] INSTANCE_HOME breaks cross products import

[Johan Carlsson]

Hi,
I'm using then the INSTANCE_HOME to have separate
Zope instances use a base zope installation and a shared 
products directory with symlink's to the instance product
folder. As described in the "How-To: Make your life easier 
with INSTANCE_HOME" by 4am.

Now the LoginManager can't import anything from the ZPattern module.

<start up error message>
2000-10-17T21:59:14 ERROR(200) Zope Couldn't import Products.LoginManager
Traceback (innermost last):
  File /bigshare/zopeservers/Zope-2.2.2-base/lib/python/OFS/Application.py, line 397, in import_products
    (Object: string)
  File /bigshare/zopeservers/unitedrings/Products/LoginManager/__init__.py, line 1, in ?
  File /bigshare/zopeservers/unitedrings/Products/LoginManager/LoginManager.py, line 9, in ?
ImportError: cannot import name SheetProviderContainer
</start up error message>

Now this works fine if I start Zope from the base Zope installation.

So what goes wrong and why? 
Does I do anything wrong or should/could this be fixed in the product?
If so I guess it would be practical to document som product author guidelines.

Regards,
Johan Carlsson