Release 0.4.2

[Totktonada]

[0.4.2]

Fixed

• Fetch schema from a replicaset leader to apply on the clusterwide config even when migrations.up() is called on a replica (Migrations may fail if started from replica #56). The local schema on the replica may be not the most actual due to replication lag.
• Issue a warning into log when register_sharding_key() is called with {'bucket_id'} key (Warn when register_sharding_key() is called with 'bucket_id' key #49). It is likely a mistake: sharding key is a set of fields, which are used to calculate bucket_id, not the bucket_id itself.