Add natural key support to the user mailer model.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/mailer/managers.py

@@ -0,0 +1,8 @@
+from __future__ import unicode_literals
+
+from django.db import models
+
+
+class UserMailerManager(models.Manager):
+    def get_by_natural_key(self, label):
+        return self.get(label=label)

mayan/apps/mailer/models.py

@@ -11,6 +11,7 @@ from django.utils.html import strip_tags
 from django.utils.module_loading import import_string
 from django.utils.translation import ugettext_lazy as _
 
+from .managers import UserMailerManager
 from .utils import split_recipient_list
 
 logger = logging.getLogger(__name__)
@@ -51,6 +52,8 @@ class UserMailer(models.Model):
         blank=True, verbose_name=_('Backend data')
     )
 
+    objects = UserMailerManager()
+
     class Meta:
         ordering = ('label',)
         verbose_name = _('User mailer')
@@ -77,6 +80,9 @@ class UserMailer(models.Model):
     def loads(self):
         return json.loads(self.backend_data)
 
+    def natural_key(self):
+        return (self.label,)
+
     def save(self, *args, **kwargs):
         if self.default:
             UserMailer.objects.select_for_update().exclude(pk=self.pk).update(