ospec-the-library should throw rather than call process.exit(1)

[pygy]

https://gitter.im/lhorie/mithril.js?at=58e4dfe48bb56c2d11797f22

This was raised by @vladpazych on gitter:

Hello everybody.
I am trying to setup ospec for tdd, but when at least one test fails - my test server exits.
Is it expected behaviour?
I do something like this:
watch(path.resolve('./test/unit'), { recursive: true }, function () {

 var _o = o.new()
 _o('addition', () => {
   _o(1 + 1).equals(2)
 })
 _o.run()
})

I tried to catch _o.run(), but there is no exception. It just stops server.

We could have ospec-the-binary call process.exit(1) instead if ospec-the-library throws

[dead-claudia]

Better: process.exitCode = 1 from the binary, and invoke an error-first callback when done.

[pygy]

Fixed by #2020