When using Wattsi server, on success, Wattsi warnings are not conveyed to the user

[domenic]

IRC chatter says so, at least.

PRs to https://github.com/domenic/wattsi-server welcome. I'll probably work on this tomorrow otherwise. Currently I'm thinking the best approach is to include an output.txt in the zip file produced by the server?

[sideshowbarker]

I think also, when we get our CI set up, it should include a step that cats that file and fails if it’s non-empty