Update databases/py-cassandra-driver to 3.7.0.

Features
- Add v5 protocol failure map
- Don't return from initial connect on first error
- Indicate failed column when deserialization fails
- Let Cluster.refresh_nodes force a token map rebuild
- Refresh UDTs after "keyspace updated" event with v1/v2 protocol
- EC2 Address Resolver
- Speculative query retries
- Expose paging state in API
- Don't mark host down while one connection is active
- Query request size information
- Avoid quadratic ring processing with invalid replication factors
- Improve Connection/Pool creation concurrency on startup
- Add beta version native protocol flag
- cqlengine: Connections: support of multiple keyspaces and
  sessions

Bug Fixes
- Race when adding a pool while setting keyspace
- Update results_metadata when prepared statement is reprepared
- CQL Export for Thrift Tables
- cqlengine: default value not applied to UserDefinedType
- cqlengine: columns are no longer hashable
- cqlengine: remove clustering keys from where clause when
  deleting only static columns

(fhajny)