Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
Add some useful things, such as error types and logcontext handling, to the
API.
Make `hs` a private member to dissuade people from using it (hopefully
they aren't already).
Add a couple of new methods (`record_user_external_id` and
`generate_short_term_login_token`).