Thanks @Half-Shot !!!

Fix incorrect truncation in get_missing_events

run the circle builds in docker containers

It's quite important that get_missing_events returns the *latest* events in the
room; however we were pulling event ids out of the database until we got *at
least* 10, and then taking the *earliest* of the results.

We also shouldn't really be relying on depth, and should be checking the
room_id.

the docker image doesn't have wget

Docker containers spin up faster than entire VMs.

- Improve logging: log things in the right order, include destination and txids
  in all log lines, don't log successful responses twice

- Fix the docstring on TransportLayerClient.send_transaction

- Don't use treq.request, which is overcomplicated for our purposes: just use a
  twisted.web.client.Agent.

- simplify the logic for setting up the bodyProducer

- fix bytes/str confusions

E2E backups

py3: python3.7 hotfixes

just some docstrings to clarify the behaviour here

Add metric to count lazy member sync requests

Log looping call exceptions

Optimisation for filter_events_for_server

We're better off hashing just the event_id than the whole ((type, state_key),
event_id) tuple - so use a dict instead of a set.

Also, iteritems > items.

Since we don't actually delete the keys, just mark the versions
as deleted in the db rather than actually deleting them, then we
won't reuse versions.

Fixes https://github.com/vector-im/riot-web/issues/7448