Log Message:
Update databases/py-cassandra-driver to 3.12.0.

Features
- Send keyspace in QUERY, PREPARE, and BATCH messages
- Add IPv4Address/IPv6Address support for inet types
- WriteType.CDC and VIEW missing
- Warn on Cluster init if contact points are specified but LBP isn't
- Include hash of result set metadata in prepared stmt id
- Add NO_COMPACT startup option
- Add new exception type for CDC

Bug Fixes
- Both _set_final_exception/result called for the same ResponseFuture
- Use of DCAwareRoundRobinPolicy raises NoHostAvailable exception
- Not create two sessions by default in CQLEngine
- Bug when subclassing AyncoreConnection
- Error at cleanup when closing the asyncore connections
- Fix sites where sessions can change during iteration
- cqlengine: allow min_length=0 for Ascii and Text column types
- Rare exception when "sys.exit(0)" after query timeouts
- Dont set the session keyspace when preparing statements
- Use of DCAwareRoundRobinPolicy raises NoHostAvailable exception

Other
- Remove DeprecationWarning when using WhiteListRoundRobinPolicy
- Bump Cython dependency version to 0.27