* Run unit tests against python 3.7

... so that we span the full range of our supported python versions

* Switch to xenial

* fix psql fail

* pep8 etc want python 3.6

Batch cache invalidation over replication

Test against Postgres 9.5 as well as 9.4

Support .well-known delegation when issuing certificates through ACME

Split /login into client_reader

* fix to use makeContext so that we don't need to rebuild the certificateoptions each time

Transfer bans on room upgrade

Postgres 9.5 is the first to support UPSERTs, so we should really run against
it as well as 9.4.

Currently whenever the current state changes in a room invalidate a lot
of caches, which cause *a lot* of traffic over replication. Instead,
lets batch up all those invalidations and send a single poke down
the replication streams.

Hopefully this will reduce load on the master process by substantially
reducing traffic.

Add basic optional sentry.io integration

Split out registration to worker

Correctly handle HttpResponseException when handling device updates

Cleanup top level request exception logging

 set CORS on .well-known URI to unbreak modular

Fix kicking guest users in worker mode

Firstly, we always logged that the request was being handled via
`JsonResource._async_render`, so we change that to use the servlet name
we add to the request.

Secondly, we pass the exception information to the logger rather than
formatting it manually. This makes it consistent with other exception
logging, allwoing logging hooks and formatters to access the exception
information.