Cryptic error when running

I've been getting a strange error multiple times (~100) when trying to run `backpack` in my project:
```
2018-01-25 14:51 node[5617] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-21)
```

The server does start and responds to requests, but I can't shake the feeling that this will cause a problem further down the line.

For context, I'm running:
- backpack-core@0.5.0
- node v8.9.4
- npm 5.6.0
- OS X 10.13.2 (high sierra)

Possibly related to [this issue on nodejs/node](https://github.com/nodejs/node/issues/15683)?

Start by reproducing the `backpack` command on OS X 10.13.2 with backpack-core@0.5.0, Node v8.9.4, and npm 5.6.0. Compare the repeated FSEvents error with the linked Node issue and verify whether it affects the running server; done means documenting the cause and impact or identifying a confirmed fix.

Written by the indexing model from the issue text.