[ATTN] If you upgraded from v2 of ZooKeeper to v3 please read this.

[Patrick Hunt]

We've found an issue with the migration tool used to migrate users from 
version 2 of ZooKeeper to version 3. This tool was provided to users who 
upgraded from the SourceForge v2 ZK, after we moved to being a 
subproject of Apache Hadoop (which is the same time that we incremented 
the version number from 2.x.y to 3.0.0 - 2+ years ago)

https://issues.apache.org/jira/browse/ZOOKEEPER-582
Please note, this only effects users who migrated their ZK data 
directory from version 2 to version 3. If you have only ever used ZK 
version 3.0.0 and later this does not effect you.

Patrick