the HBTreeFolder2 product should not be mandatory

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@16298 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Core/Folder.py

@@ -47,10 +47,14 @@ try:
 except ImportError:
   from Products.BTreeFolder2.CMFBTreeFolder import CMFBTreeFolder
 
-from Products.BTreeFolder2.BTreeFolder2 import BTreeFolder2Base
+try:
+  from Products.HBTreeFolder2.CMFHBTreeFolder import CMFHBTreeFolder
+except ImportError:
+  class CMFHBTreeFolder:
+
+    def __init__(self, *args, **kw):
+      raise ValueError, 'You must install the HBTreeFolder2 Product'
 
-from Products.HBTreeFolder2.CMFHBTreeFolder import CMFHBTreeFolder
-from Products.HBTreeFolder2.HBTreeFolder2 import HBTreeFolder2Base
 
 from AccessControl import getSecurityManager
 from Products.ERP5Type import Permissions