If not license specified Mock-Build fails silently

[tommrr]

If the project.json is missing the license tag then when running mock build on the generated spec from Speculate, will silently fail with no error.

[niklasR]

Happy to take a PR.
(Though I'd recommend to set { "license": "UNLICENSED" } or something and be explicit about it if you don't have a licence, rather than omitting the key)

[owenj62]

I've also just spent a day debugging this issue

[njh]

If created a PR that throws an error much earlier in the process, would that make things better?

Maybe with a error message saying "please set license to 'UNLICENSED'" if this is not Open Source software.