erp5_base: use type based method to retrieve method to create posts

bt5/erp5_base/SkinTemplateItem/portal_skins/erp5_base/Entity_sendEmail.py

@@ -29,7 +29,7 @@ mail_message = portal.Base_createMailMessageAsString(
   embedded_file_list=embedded_file_list,
   extra_header_dict=extra_header_dict)
 
-create_post_message_method = getattr(event, 'Event_createPostMessage', None)
+create_post_message_method = event.getTypeBasedMethod('createPostMessage')
 if create_post_message_method:
   create_post_message_method(mail_message)
 else:

bt5/erp5_base/SkinTemplateItem/portal_skins/erp5_base/MailMessage_send.py

@@ -48,7 +48,7 @@ if not context.hasStartDate():
 
 if download or not use_activity:
 
-  create_post_message_method = getattr(context, 'Event_createPostMessage', None)
+  create_post_message_method = context.getTypeBasedMethod('createPostMessage')
 
   for to_url in to_url_list:
     body = body or context.getTextContent() or ''