Merge branch 'develop' of github.com:matrix-org/synapse into release-v0.17.1

synapse/appservice/scheduler.py

synapse/crypto/keyring.py

synapse/federation/federation_base.py

synapse/federation/federation_client.py

synapse/handlers/appservice.py

synapse/handlers/federation.py

synapse/handlers/message.py

synapse/handlers/room_member.py

synapse/handlers/typing.py

synapse/notifier.py

synapse/push/push_tools.py

synapse/push/pusherpool.py

synapse/rest/client/v1/room.py

synapse/rest/client/v2_alpha/register.py

synapse/storage/events.py

synapse/storage/schema/delta/34/received_txn_purge.py

synapse/storage/stream.py

synapse/storage/transactions.py

synapse/util/async.py

synapse/util/logcontext.py