Replace _constraints with validate in ModelStorage and improve user messages.

issue2616
review371002

company.py

@@ -30,13 +30,11 @@ class Company(ModelSQL, ModelView):
     @classmethod
     def __setup__(cls):
         super(Company, cls).__setup__()
-        cls._constraints += [
-            ('check_recursion', 'recursive_companies'),
-            ]
-        cls._error_messages.update({
-                'recursive_companies': (
-                    'You can not create recursive companies!'),
-                })
+
+    @classmethod
+    def validate(cls, companies):
+        super(Company, cls).validate(companies)
+        cls.check_recursion(companies)
 
     @classmethod
     def copy(cls, companies, default=None):

company.xml

@@ -391,5 +391,15 @@ this repository contains the full copyright notices and license terms. -->
             <field name="model">party.party,-1</field>
             <field name="action" ref="report_letter"/>
         </record>
+
+        <record model="ir.translation" id="company_recursion_error">
+            <field name="name">company.company</field>
+            <field name="lang">en_US</field>
+            <field name="type">error</field>
+            <field name="src">recursion_error</field>
+            <field name="value">Recursion error: Company "%(rec_name)s" with parent "%(parent_rec_name)s" was configured as ancestor of itself.</field>
+            <field name="module">company</field>
+            <field name="fuzzy" eval="False"/>
+        </record>
     </data>
 </tryton>