Use PySON

product.py

@@ -1,9 +1,10 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of
 #this repository contains the full copyright notices and license terms.
 from trytond.model import ModelView, ModelSQL, fields
+from trytond.pyson import Not, Bool, Eval
 
 STATES = {
-    'readonly': "active == False",
+    'readonly': Not(Bool(Eval('active'))),
 }
 
 

product.xml

@@ -165,8 +165,8 @@ this repository contains the full copyright notices and license terms. -->
             <field name="name">Product by Category</field>
             <field name="res_model">product.product</field>
             <field name="view_type">form</field>
-            <field name="context">{'categories': [active_id]}</field>
-            <field name="domain">[('category','child_of', [active_id], 'parent')]</field>
+            <field name="context">{'categories': [Eval('active_id')]}</field>
+            <field name="domain">[('category','child_of', [Eval('active_id')], 'parent')]</field>
         </record>
         <record model="ir.action.act_window.view" id="act_product_by_category_view1">
             <field name="sequence" eval="10"/>

uom.py

@@ -2,10 +2,11 @@
 #this repository contains the full copyright notices and license terms.
 from trytond.model import ModelView, ModelSQL, fields
 from trytond.model.modelstorage import OPERATORS
+from trytond.pyson import Not, Bool, Eval
 from decimal import Decimal
 
 STATES = {
-    'readonly': "(active == False)",
+    'readonly': Not(Bool(Eval('active'))),
 }
 
 class UomCategory(ModelSQL, ModelView):