diff --git a/exceptions.py b/exceptions.py
new file mode 100644
index 0000000000..f5c83d762d
--- /dev/null
+++ b/exceptions.py
@@ -0,0 +1,8 @@
+# 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.exceptions import UserWarning
+
+
+class PurchaseWarning(UserWarning):
+    pass
diff --git a/message.xml b/message.xml
new file mode 100644
index 0000000000..c100533d83
--- /dev/null
+++ b/message.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
+this repository contains the full copyright notices and license terms. -->
+<tryton>
+    <data group="1">
+        <record model="ir.message" id="msg_pending_purchase_done">
+            <field name="text">The productions "%(productions)s" cannot be processed as they have pending purchases.</field>
+        </record>
+    </data>
+</tryton>
diff --git a/production.py b/production.py
index f281412b3c..d85c7a3f24 100644
--- a/production.py
+++ b/production.py
@@ -4,10 +4,13 @@ import hashlib
 from decimal import Decimal
 from itertools import groupby
 
+from trytond.i18n import gettext
 from trytond.model import ModelView, Workflow, fields
 from trytond.pool import PoolMeta, Pool
 from trytond.pyson import Eval, Bool, If
 
+from .exceptions import PurchaseWarning
+
 
 class Routing(metaclass=PoolMeta):
     __name__ = 'production.routing'
@@ -100,15 +103,6 @@ class Production(metaclass=PoolMeta):
         depends=['company'],
         help="The lines to add to the production cost.")
 
-    @classmethod
-    def __setup__(cls):
-        super(Production, cls).__setup__()
-        cls._error_messages.update({
-                'pending_purchase_done': (
-                    'The productions "%s" can not be done '
-                    'as they have pending purchases'),
-                })
-
     def get_cost(self, name):
         pool = Pool()
         Currency = pool.get('currency.currency')
@@ -218,6 +212,9 @@ class Production(metaclass=PoolMeta):
     @ModelView.button
     @Workflow.transition('done')
     def done(cls, productions):
+        pool = Pool()
+        Warning = pool.get('res.user.warning')
+
         def pending_purchase(production):
             return any(l.purchase_state in {'draft', 'quotation'}
                 for l in production.purchase_lines)
@@ -228,6 +225,9 @@ class Production(metaclass=PoolMeta):
                 names += '...'
             warning_name = '%s.pending_purchase.done' % hashlib.md5(
                 str(pendings).encode('utf-8')).hexdigest()
-            cls.raise_user_warning(
-                warning_name, 'pending_purchase_done', names)
+            if Warning.check(warning_name):
+                raise PurchaseWarning(
+                    warning_name,
+                    gettext('production_outsourcing.msg_pending_purchase_done',
+                        productions=names))
         super(Production, cls).done(productions)
diff --git a/tests/scenario_production_outsourcing.rst b/tests/scenario_production_outsourcing.rst
index d8cf6df5b4..fb5ddd7373 100644
--- a/tests/scenario_production_outsourcing.rst
+++ b/tests/scenario_production_outsourcing.rst
@@ -153,7 +153,7 @@ Try to do the production with pending purchase::
     >>> production.click('done')  # doctest: +IGNORE_EXCEPTION_DETAIL
     Traceback (most recent call last):
         ...
-    UserWarning: ...
+    PurchaseWarning: ...
 
 Validate the purchase::
 
diff --git a/tryton.cfg b/tryton.cfg
index 2c7dcb201b..cc1bb79cb1 100644
--- a/tryton.cfg
+++ b/tryton.cfg
@@ -9,3 +9,4 @@ depends:
 xml:
     production.xml
     purchase.xml
+    message.xml