Fix pep8 codestyle warnings

synapse/api/auth.py

synapse/api/events/validator.py

synapse/app/homeserver.py

synapse/app/synctl.py

synapse/federation/replication.py

synapse/federation/units.py

synapse/handlers/directory.py

synapse/handlers/federation.py

synapse/handlers/message.py

synapse/handlers/room.py

synapse/http/content_repository.py

synapse/http/server.py

synapse/notifier.py

synapse/rest/events.py

synapse/storage/_base.py

synapse/storage/registration.py

synapse/storage/room.py

synapse/storage/signatures.py

synapse/storage/stream.py

synapse/util/__init__.py