fixup! fixup! fixup! fix SyntaxWarning

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Base_validateRelation.py

@@ -77,7 +77,7 @@ try:
     if checkFieldType(my_field, 'MultiRelationStringField'):
       # The checkProperty sometimes does not provide an
       # acceptable value - XXXX - see vetement_id in Modele View
-      if old_value is '' or old_value is None:
+      if old_value == '' or old_value is None:
         old_value = []
       try:
         old_value = list(old_value)

product/ERP5Type/Core/ContentExistenceConstraint.py

@@ -76,7 +76,7 @@ class ContentExistenceConstraint(ConstraintMixin):
 
     # Otherwise, generate an error message
     mapping = {}
-    if portal_type is ():
+    if not portal_type:
       message_id = 'message_no_subobject'
     else:
       message_id = 'message_no_subobject_portal_type'