Use Generic Setup for defining versioning policies

If you activated versioning for your custom content types you most likely followed one of these How-Tos:

• Enabling versioning on your custom content-types

• History and Versioning
  

Both basically recommend to set the versioning policies CMFEditions is using in a custom setuphandler:

from Products.CMFEditions.setuphandlers import DEFAULT_POLICIES

portal_repository = getToolByName(portal, 'portal_repository')
versionable_types = list(portal_repository.getVersionableContentTypes())

for type_id in ['MyType', 'AnotherType']:
    if type_id not in versionable_types:
        versionable_types.append(type_id)
        # Add default versioning policies to the versioned type
        for policy_id in DEFAULT_POLICIES:
            portal_repository.addPolicyForContentType(type_id, policy_id)
portal_repository.setVersionableContentTypes(versionable_types)

when migrating to plone4.1 you'll get the following error:

ImportError: cannot import name DEFAULT_POLICIES

To make your Product compatible with Plone4.1 you can remove the code for setting versionableContenttypes above and simply add a file named repositorytool.xml to your package's Generic Setup profile and you're done:

<?xml version="1.0"?>
<repositorytool>
    <policymap>
        <type name="MyType">
            <policy name="at_edit_autoversion"/>
            <policy name="version_on_revert"/>
        </type>
        <type name="AnotherType">
            <policy name="at_edit_autoversion"/>
            <policy name="version_on_revert"/>
        </type>
    </policymap>
</repositorytool>

If you need to be backward compatible you can add repositorytool.xml (which will be used in plone >= 4.1) and add a condition to your setupandler. eg:

try:
    from Products.CMFEditions.setuphandlers import DEFAULT_POLICIES
    # we're on plone < 4.1, configure versionable types manually
    setVersionedTypes(portal)
except ImportError:
    # repositorytool.xml will be used
    pass