// for example there are no Go files (NoGoError), or there's a problem in the imported
	// package's source files themselves (scanner errors).
	//
	// TODO(matloob): Perhaps make each of those the errors in the first group
	// (including modload.ImportMissingError, ImportMissingSumError, and the
	// corresponding "cannot find package %q in any of" GOPATH-mode error

	handle := func(ctx context.Context, a *Action) {
		if a.json != nil {
			a.json.TimeStart = time.Now()
		}
		var err error
		if a.Actor != nil && (!a.Failed || a.IgnoreFail) {
			// TODO(matloob): Better action descriptions
			desc := "Executing action (" + a.Mode
			if a.Package != nil {
				desc += " " + a.Package.Desc()
			}
			desc += ")"
			ctx, span := trace.StartSpan(ctx, desc)