debug mailing list

models/mailing_list.py

@@ -89,7 +89,7 @@ class MailingContact(models.Model):
 
     def create_sendinblue_contact(self):
             _logger.error('create_sendinblue_contact')
-            _logger.error(str(self.email)+' '+ self.list_ids)
+            _logger.error(str(self.email)+' '+ str(self.list_ids))
             if self.email and self.list_ids:
                 _logger.error('create_sendinblue_contact -1')
                 configuration = sib_api_v3_sdk.Configuration()