zerver.lib.initial_password.initial_password is supposed to return an
Optional[text_type], but it returns an Optional[binary_type] instead.
Encode the return value to make sure it returns an Optional[text_type].
Also, fixed up the annotations for tornadoviews to better align with
how narrows was defined as `Iterable[Sequence[str]]` rather than
`List[Tuple[str, str]]`.
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)