Merge remote-tracking branch 'upstream/master' into feat-dockerfile

CHANGES.rst

UPGRADE.rst

docs/workers.rst

scripts/synapse_port_db

synapse/__init__.py

synapse/api/errors.py

synapse/app/appservice.py

synapse/app/client_reader.py

synapse/app/event_creator.py

synapse/app/federation_reader.py

synapse/app/federation_sender.py

synapse/app/frontend_proxy.py

synapse/app/homeserver.py

synapse/app/media_repository.py

synapse/app/pusher.py

synapse/app/synchrotron.py

synapse/app/synctl.py

synapse/app/user_dir.py

synapse/federation/transport/client.py

synapse/federation/transport/server.py