[FIX] models: Always use MissingError when a document is missing

As done in write and already in next version (see 0fd773a), accessing a deleted
record (through read or check access rights) should always return a MissingError
instead of the generic except_orm.
This will allow code ignoring deleted record (e.g. 'recompute' method) to safely
process the other records.
Fixes #6105

openerp/models.py

@@ -3470,8 +3470,8 @@ class BaseModel(object):
                     # errors for non-transactional search/read sequences coming from clients
                     return
                 _logger.warning('Failed operation on deleted record(s): %s, uid: %s, model: %s', operation, uid, self._name)
-                raise except_orm(_('Missing document(s)'),
-                                 _('One of the documents you are trying to access has been deleted, please try again after refreshing.'))
+                raise MissingError(
+                    _('One of the documents you are trying to access has been deleted, please try again after refreshing.'))
 
 
     def check_access_rights(self, cr, uid, operation, raise_exception=True): # no context on purpose.