ConsistencyMessage: Make Constraint Usage facultative

product/ERP5Type/ConsistencyMessage.py

@@ -46,17 +46,21 @@ class ConsistencyMessage(ObjectMessage):
     init specific variable to constraint
     """
     ObjectMessage.__init__(self, object_relative_url, message, mapping)
-    self.description = constraint.description
-    self.class_name = constraint.__class__.__name__
-    # keep track of the relative URL of the constraint to have it included in
-    # the message
-    constraint_relative_url = getattr(aq_base(constraint), 'relative_url', None)
-    if not constraint_relative_url:
-      try:
-        constraint_relative_url = constraint.getRelativeUrl()
-      except AttributeError:
-        constraint_relative_url = constraint.id
-    self.constraint_relative_url = constraint_relative_url
+    self.description = ""
+    self.class_name = "Constraint Message"
+    self.constraint_relative_url = ""
+    if constraint:
+      self.description = constraint.description
+      self.class_name = constraint.__class__.__name__
+      # keep track of the relative URL of the constraint to have it included in
+      # the message
+      constraint_relative_url = getattr(aq_base(constraint), 'relative_url', None)
+      if not constraint_relative_url:
+        try:
+          constraint_relative_url = constraint.getRelativeUrl()
+        except AttributeError:
+          constraint_relative_url = constraint.id
+      self.constraint_relative_url = constraint_relative_url
 
     self.__dict__.update(kw)