[FIX] base: translate _constraint message

While the error content is automatically translatable, the header was not.

Fixes #5645

openerp/addons/base/i18n/base.pot

@@ -8148,6 +8148,12 @@ msgstr ""
 msgid "Error details:"
 msgstr ""
 
+#. module: base
+#: code:addons/models.py:1281
+#, python-format
+msgid "Error while validating constraint"
+msgstr ""
+
 #. module: base
 #: constraint:res.company:0
 msgid "Error! You can not create recursive companies."

openerp/models.py

@@ -1278,7 +1278,7 @@ class BaseModel(object):
                 except ValidationError, e:
                     raise
                 except Exception, e:
-                    raise ValidationError("Error while validating constraint\n\n%s" % tools.ustr(e))
+                    raise ValidationError("%s\n\n%s" % (_("Error while validating constraint"), tools.ustr(e)))
 
     @api.model
     def default_get(self, fields_list):