Rename delete_rule -> reverse_delete_rule.

mongoengine/base.py

@@ -191,7 +191,7 @@ class DocumentMetaclass(type):
         new_class = super_new(cls, name, bases, attrs)
         for field in new_class._fields.values():
             field.owner_document = new_class
-            delete_rule = getattr(field, 'delete_rule', DO_NOTHING)
+            delete_rule = getattr(field, 'reverse_delete_rule', DO_NOTHING)
             if delete_rule != DO_NOTHING:
                 field.document_type.register_delete_rule(new_class, field.name,
                         delete_rule)

mongoengine/fields.py

@@ -418,13 +418,13 @@ class ReferenceField(BaseField):
     access (lazily).
     """
 
-    def __init__(self, document_type, delete_rule=DO_NOTHING, **kwargs):
+    def __init__(self, document_type, reverse_delete_rule=DO_NOTHING, **kwargs):
         if not isinstance(document_type, basestring):
             if not issubclass(document_type, (Document, basestring)):
                 raise ValidationError('Argument to ReferenceField constructor '
                                       'must be a document class or a string')
         self.document_type_obj = document_type
-        self.delete_rule = delete_rule
+        self.reverse_delete_rule = reverse_delete_rule
         super(ReferenceField, self).__init__(**kwargs)
 
     @property