code: func makeRPCFriendlyDiag(diag Diagnostic) Diagnostic {
  	desc := diag.Description()
  	source := diag.Source()
  	return &rpcFriendlyDiag{
  		Severity_: diag.Severity(),
  		Summary_:  desc.Summary,
  		Detail_:   desc.Detail,
  		Subject_:  source.Subject,
  		Context_:  source.Context,
  	}
  }
docs: // rpcFriendlyDiag transforms a given diagnostic so that is more friendly to
  // RPC.
  //
  // In particular, it currently returns an object that can be serialized and
  // later re-inflated using gob. This definition may grow to include other
  // serializations later.