We have to read the data anyway, and we don't have a convenient file
handle for uploads from attachments sent through the e-mail gateway.
(imported from commit 86260a4eaceef85c82707929a80558e11dc54ef6)
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)