Bugfixes

• Close leaked selector in version check (dpkp #1425)
• Fix BrokerConnection.connection_delay() to return milliseconds (dpkp #1414)
• Use local copies in Fetcher._fetchable_partitions to avoid mutation errors (dpkp #1400)
• Fix error var name in _unpack (j2gg0s #1403)
• Fix KafkaConsumer compacted offset handling (dpkp #1397)
• Fix byte size estimation with kafka producer (blakeembrey #1393)
• Fix coordinator timeout in consumer poll interface (braedon #1384)

Client

• Add BrokerConnection.connect_blocking() to improve bootstrap to multi-address hostnames (dpkp #1411)
• Short-circuit BrokerConnection.close() if already disconnected (dpkp #1424)
• Only increase reconnect backoff if all addrinfos have been tried (dpkp #1423)
• Make BrokerConnection .host / .port / .afi immutable to avoid incorrect 'metadata changed' checks (dpkp #1422)
• Connect with sockaddrs to support non-zero ipv6 scope ids (dpkp #1433)
• Check timeout type in KafkaClient constructor (asdaraujo #1293)
• Update string representation of SimpleClient (asdaraujo #1293)
• Do not validate api_version against known versions (dpkp #1434)

Consumer

• Avoid tight poll loop in consumer when brokers are down (dpkp #1415)
• Validate max_records in KafkaConsumer.poll (dpkp #1398)
• KAFKA-5512: Awake heartbeat thread when it is time to poll (dpkp #1439)

Producer

• Validate that serializers generate bytes-like (or None) data (dpkp #1420)

Core / Protocol

• Support alternative lz4 package: lz4framed (everpcpc #1395)
• Use hardware accelerated CRC32C function if available (tvoinarovskyi #1389)
• Add Admin CreatePartitions API call (alexef #1386)

Test Infrastructure

• Close KafkaConsumer instances during tests (dpkp #1410)
• Introduce new fixtures to prepare for migration to pytest (asdaraujo #1293)
• Removed pytest-catchlog dependency (asdaraujo #1380)
• Fixes racing condition when message is sent to broker before topic logs are created (asdaraujo #1293)
• Add kafka 1.0.1 release to test fixtures (dpkp #1437)

Logging / Error Messages

• Re-enable logging during broker version check (dpkp #1430)
• Connection logging cleanups (dpkp #1432)
• Remove old CommitFailed error message from coordinator (dpkp #1436)