Created by: gaearon
This should include some error handling that would work around https://github.com/facebookincubator/create-react-app/issues/3690.
I haven't verified it works yet, but the last time I tried to do similar edits locally, and then inserted a throw in the same place the error was reported, detect-port said the ports were taken and jumped to a high port. I'm not sure why it didn't give me an error instead but this seems edge casey enough that I don't care strongly how it works as long as it doesn't crash.