Failure to encode log message as JSON

[jkozlowski]

Internal product is hitting issues trying to log line in AsyncTimeLockUnlocker:

WARN Failed to json encode an object of type [java.util.HashSet] from INFO com.palantir.lock.client.AsyncTimeLockUnlocker: 'Failed to unlock lock tokens {} from timelock. They will eventually expire on their own, but if this message recurs frequently, it may be worth investigation.

[jkozlowski]

Seeing similar thing for loglines in CassandraClientPoolingContainer when trying to serialize CassandrClient