#416 Plone migration error for 'GroupUserFolder'

[Praful Kapadia]

When trying to migrate a 3.3.5 Plone site to 4.2, the following error occurs during a dry run of the upgrade:

...
Ran upgrade step: Upgrade DCMI metadata storage in portal_metadata
Upgrade aborted. Error:
Traceback (most recent call last):
File "c:\plone42\eggs\products.cmfplone-4.2.1.1-py2.6.egg\Products\CMFPlone\MigrationTool.py", line 178, in upgrade
step['step'].doStep(setup)
File "c:\plone42\eggs\products.genericsetup-1.7.2-py2.6.egg\Products\GenericSetup\upgrade.py", line 140, in doStep
self.handler(tool)
File "c:\plone42\eggs\plone.app.upgrade-1.2.1-py2.6.egg\plone\app\upgrade\v40\alphas.py", line 490, in addRecursiveGroupsPlugin
plugins = acl.plugins
AttributeError: 'GroupUserFolder' object has no attribute 'plugins'

Please can you provide advice