Convert panic (and any console.log) errors to panicOnBuild if the error should stop a build from succeeding

[KyleAMathews]

/cc @jquense

[anjawaldbauer]

@KyleAMathews Is my understanding correct that you want Gatsby v2 to stop a build on any error or warning? This is exactly what I would want. I would love to help implement this, if you could give a little bit of guidance. I would also very much appreciate if you could explain how to do implement this behavior in Gatsby v1 as an opt-in. Thank you in advance!

[m-allanson]

@anjawaldbauer This has been implemented in v2 as a panicOnBuild method of the reporter. I don't think there are any plans to backport it to v1, as that effort could be spent getting v2 out more quickly :)

[KyleAMathews]

Yeah, let's close this. It won't be back-ported. There's still work to sort out which errors/warnings should use this but that can be an on-going project.