Use root user to evaluate user environment

The user attributes may be restricted by other record rules so to evaluate the
domain, we must have access to all attributes.

issue9901
review333341002

trytond/ir/rule.py

@@ -136,8 +136,10 @@ class Rule(ModelSQL, ModelView):
     @staticmethod
     def _get_context():
         User = Pool().get('res.user')
-        user_id = Transaction().user
-        with Transaction().set_context(_check_access=False, _datetime=None):
+        transaction = Transaction()
+        user_id = transaction.user
+        with transaction.set_context(_check_access=False, _datetime=None), \
+                transaction.set_user(0):
             user = EvalEnvironment(User(user_id), User)
         return {
             'user': user,