After failing to notice a place where we wanted to hide timezone
information, we decided to add timezones to some of the test
users, so that we can better consider the effects of timezones
when manually testing.
Testing:
* ran populate_db and confirmed users had timezones in the UI
* updated test_populate_db.py
We don't have to go to the database to get the Recipient
fields for `user_profile.recipient`.
See also 85ed6f332a from a little
over a year ago--it's very similar.
This fixes a batch of mypy errors of the following format:
'Item "None" of "Optional[Something]" has no attribute "abc"
Since we have already been recklessly using these attritbutes
in the tests, adding assertions beforehand is justified presuming
that they oughtn't to be None.