Hack: Serialize document module

When running multiple parralel ingestion updating documents inplace,
manage_delObjects complains that object is already removed (which is not the
case)

product/ERP5/Document/Document.py

@@ -634,6 +634,9 @@ class Document(DocumentExtensibleTraversableMixin, XMLObject, UrlMixin,
             if k not in FIXED_PROPERTY_IDS and self.hasProperty(k):
               update_kw[k] = self.getProperty(k)
           existing_document.edit(**update_kw)
+          self.getParentValue().serialize()
+          import transaction
+          transaction.savepoint(optimistic=True)
           # Erase self
           self.getParentValue().manage_delObjects([self.getId(),])
     return document