See https://uberchromegw.corp.google.com/i/chromium.linux/builders/Android%20Tests/builds/46125 / https://chromium-swarm.appspot.com/task?id=38bd04b999969510&refresh=10&show_raw=1:

[W2017-09-21T11:53:33.892159Z 21245 0 pubsubOutput.go:217] TRANSIENT error publishing messages; retrying... {"error":"context deadline exceeded", "delay":"30s", "pubsub":"pubsub(projects/luci-logdog/topics/logs)"}

Until at the end the process is killed.