sbt "project gearpump-examples-wordcount" run failed with ClassNotFoundException

[manuzhang]

[error] (run-main-0) java.lang.ClassNotFoundException: scala.Int
[INFO] [12/15/2018 19:23:44.474] [RemoteActorRefProvider$RemotingTerminator] Shutting down remote daemon.
[INFO] [12/15/2018 19:23:44.477] [RemoteActorRefProvider$RemotingTerminator] Remote daemon shut down; proceeding with flushing remote transports.
[INFO] [12/15/2018 19:23:44.511] [RemoteActorRefProvider$RemotingTerminator] Remoting shut down.
[error] java.lang.ClassNotFoundException: scala.Int
[error] Nonzero exit code: 1
[error] (Compile / run) Nonzero exit code: 1
[error] Total time: 6 s, completed Dec 15, 2018 7:23:44 PM