What does this error mean?

This error means an InterruptedException occurred during a forced shutdown  (e.g. nodetool stop COMPACTION) of a compaction process.

Why does this error occur?

This error occurs if a thread is interrupted during a CompactionManager.forceShutdown call.

How do you fix this error?

This error should not occur from within Cassandra because Cassandra does not interrupt threads. Further investigation is necessary and a ticket should be filed with DataStax Support.