[manual] Rename Django app from zephyr to zerver.

This needs to be deployed to both staging and prod at the same
off-peak time (and the schema migration run).

At the time it is deployed, we need to make a few changes directly in
the database:

(1) UPDATE django_content_type set app_label='zerver' where app_label='zephyr';
(2) UPDATE south_migrationhistory set app_name='zerver' where app_name='zephyr';

(imported from commit eb3fd719571740189514ef0b884738cb30df1320)

zerver/management/commands/delete_tutorial_streams.py

@@ -0,0 +1,53 @@
+from __future__ import absolute_import
+
+from django.core.management.base import BaseCommand
+from zerver.models import Subscription, Recipient, Message, Stream, \
+    get_user_profile_by_email
+from django.db.models import Q
+
+import datetime
+import pytz
+from optparse import make_option
+
+class Command(BaseCommand):
+    help = """Delete all inactive tutorial stream subscriptions."""
+
+    option_list = BaseCommand.option_list + (
+        make_option('-f', '--for-real',
+                    dest='for_real',
+                    action='store_true',
+                    default=False,
+                    help="Actually deactive subscriptions. Default is a dry run."),
+        )
+
+    def has_sent_to(self, user_profile, recipient):
+        return Message.objects.filter(sender=user_profile, recipient=recipient).count() != 0
+
+    def handle(self, **options):
+        possible_tutorial_streams = Stream.objects.filter(Q(name__startswith='tutorial-'))
+
+        tutorial_bot = get_user_profile_by_email("tutorial-bot@zulip.com")
+
+        for stream in possible_tutorial_streams:
+            recipient = Recipient.objects.get(type=Recipient.STREAM, type_id=stream.id)
+            subscribers = Subscription.objects.filter(recipient=recipient, active=True)
+            if ((subscribers.count() == 1) and self.has_sent_to(tutorial_bot, recipient)):
+                # This is a tutorial stream.
+                most_recent_message = Message.objects.filter(
+                    recipient=recipient).latest("pub_date")
+                # This cutoff must be more generous than the tutorial bot cutoff
+                # in the client code.
+                cutoff = datetime.datetime.now(tz=pytz.utc) - datetime.timedelta(hours=2)
+
+                if most_recent_message.pub_date < cutoff:
+                    # The tutorial has expired, so delete the stream.
+                    print stream.name, most_recent_message.pub_date
+                    if options["for_real"]:
+                        tutorial_user = subscribers[0]
+                        tutorial_user.active = False
+                        tutorial_user.save(update_fields=["active"])
+
+        if options["for_real"]:
+            print "Subscriptions deactivated."
+        else:
+            print "This was a dry run. Pass -f to actually deactivate."