A later commit alters `authenticate` of EmailAuthBackend to
add a store `needs_to_change_password` variable to session
which is useful to insist users on changing their weak password.
The tests start failing with that change because client.login()
runs `authenticate` without a `request` object. So, this commit
sends a request object with `request.session=self.client.session`
to self.client.login() in tests wherever needed.