[MERGE] mail: avoid obscure failure when processing batches of emails with attachments

This issue was caused by the way browse_records are cached,
  in combination with the deletion of messages just after sending
  them. When processing a second message, the attachment.datas
  function fields gets computed for all messages that are being
  browsed, including the first message that was already deleted,
  causing an exception. The value of the function field had 
  already been computed for the first message, but had been
  discarded by the message.refresh() call.
  Hopefully this kind of issue will disappear once we implement
  the new ORM API.

bzr revid: odo@openerp.com-20120622152536-42b2s28lvdv3odyr

addons/mail/mail_message.py

@@ -518,12 +518,13 @@ class mail_message(osv.osv):
                                                 context=context)
                 if res:
                     message.write({'state':'sent', 'message_id': res})
+                    message_sent = True
                 else:
                     message.write({'state':'exception'})
+                    message_sent = False
 
                 # if auto_delete=True then delete that sent messages as well as attachments
-                message.refresh()
-                if message.state == 'sent' and message.auto_delete:
+                if message_sent and message.auto_delete:
                     self.pool.get('ir.attachment').unlink(cr, uid,
                                                           [x.id for x in message.attachment_ids \
                                                                 if x.res_model == self._name and \