add missing import

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@35745 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/mixin/document.py

@@ -27,7 +27,7 @@
 #
 ##############################################################################
 from Products.CMFCore.utils import getToolByName
-from AccessControl import ClassSecurityInfo
+from AccessControl import ClassSecurityInfo, Unauthorized
 from Products.ERP5Type import Permissions
 from OFS.Image import Pdata
 from cStringIO import StringIO