Different --silent use case

[eviefp]

This is different from #261 and #290 due to the reasoning. I would like to be able to parse the result of pulp build -- --json-errors. So the idea would be to only silence anything that pulp adds on top of purs.

One example would be, if I'm doing a large refactor by updating a constructor or something. Most likely, that would yield quite a few errors which are quite verbose. I would much rather just see a simple list of file, module and line or something.

I'm sure there are other uses for parsing the compiler output for the whole project.