Node version 12 depracated OutgoingMessage.prototype._headers, which is used in http-server. Issue is listed at:
https://github.com/http-party/http-server/issues/537
https://nodejs.org/api/deprecations.html#deprecations_dep0066_outgoingmessage_prototype_headers_outgoingmessage_prototype_headernames
Using node 12.0.0 I get the same error using http-server. Switching to 10.11.0 removes the error.