Since nodejs@10.1, the test suite (npm run test-travis) has started emitting thousands of instances of:

(node:2877) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 2 error listeners added. Use emitter.setMaxListeners() to increase limit

I am not sure if this is indicative of a real regression in nodejs production usage, but it is definitely breaking the build (https://travis-ci.org/optimizely/javascript-sdk/jobs/381767712), and can be reproduced on my Mac using nvm install 10.1.

This wasn't/isn't an issue on nodejs@10.0 (https://travis-ci.org/optimizely/javascript-sdk/jobs/376595175)