I've seen this fail in a few different PRs for different contributors, and its causing some issues during the presubmit process.. This is a multithreadred test with a lot of sleeps, so it looks a bit suspicious as the source of the problem. https://builds.apache.org/job/beam_PreCommit_Java_Commit/3688/testReport/org.apache.beam.sdk.io/FileIOTest/testMatchWatchForNewFiles/
I filed a JIRA for this issue: https://jira.apache.org/jira/browse/BEAM-6491?filter=-2
