Use auto_now_add for the lock_manager app

mayan/apps/lock_manager/models.py

@@ -2,14 +2,13 @@ from __future__ import absolute_import
 
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
-from django.utils.timezone import now
 
 from .managers import LockManager
 from .settings import DEFAULT_LOCK_TIMEOUT
 
 
 class Lock(models.Model):
-    creation_datetime = models.DateTimeField(verbose_name=_(u'Creation datetime'))
+    creation_datetime = models.DateTimeField(verbose_name=_(u'Creation datetime'), auto_now_add=True)
     timeout = models.IntegerField(default=DEFAULT_LOCK_TIMEOUT, verbose_name=_(u'Timeout'))
     name = models.CharField(max_length=48, verbose_name=_(u'Name'), unique=True)
 
@@ -19,7 +18,6 @@ class Lock(models.Model):
         return self.name
 
     def save(self, *args, **kwargs):
-        self.creation_datetime = now()
         if not self.timeout and not kwargs.get('timeout'):
             self.timeout = DEFAULT_LOCK_TIMEOUT