zilencer: Add auto_now to RemoteZulipServer.last_updated.

This should simplify the logic needed to create one of these.

zilencer/migrations/0003_add_default_for_remotezulipserver_last_updated_field.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.5 on 2017-05-16 00:03
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('zilencer', '0002_remote_zulip_server'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='remotezulipserver',
+            name='last_updated',
+            field=models.DateTimeField(auto_now=True, verbose_name='last updated'),
+        ),
+    ]

zilencer/models.py

@@ -15,7 +15,7 @@ class RemoteZulipServer(models.Model):
 
     hostname = models.CharField(max_length=128, unique=True)  # type: Text
     contact_email = models.EmailField(blank=True, null=False)  # type: Text
-    last_updated = models.DateTimeField('last updated')  # type: datetime.datetime
+    last_updated = models.DateTimeField('last updated', auto_now=True)  # type: datetime.datetime
 
 # Variant of PushDeviceToken for a remote server.
 class RemotePushDeviceToken(zerver.models.AbstractPushDeviceToken):