Ensure records are readable also for constraints

review595004

trytond/model/modelstorage.py

@@ -863,6 +863,10 @@ class ModelStorage(Model):
             with Transaction().set_user(Transaction().context.get('user')):
                 return cls._validate(cls.browse(records))
 
+        # Ensure that records are readable
+        with Transaction().set_user(0, set_context=True):
+            records = cls.browse(records)
+
         for record in records:
             record.pre_validate()
 
@@ -897,10 +901,6 @@ class ModelStorage(Model):
             return False
 
         with Transaction().set_context(ctx_pref):
-            # Ensure that records are readable
-            with Transaction().set_user(0, set_context=True):
-                records = cls.browse(records)
-
             for field_name, field in cls._fields.iteritems():
                 if isinstance(field, fields.Function) and \
                         not field.setter: