Remove unused import

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@45752 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/AttributeBlacklistedConstraint.py

@@ -26,7 +26,6 @@
 #
 ##############################################################################
 
-from Products.ERP5Type.mixin.constraint import ConstraintMixin
 from Products.ERP5Type import PropertySheet
 from Products.ERP5Type.Utils import createExpressionContext
 from Products.ERP5Type.Utils import evaluateExpressionFromString