func (i *ImportRestriction) ForbiddenImportsFor(pkg Package) ([]string, error) {
	if restricted, err := i.isRestrictedDir(pkg.Dir); err != nil {
		return []string{}, err
	} else if !restricted {
		return []string{}, nil
	}

	return i.forbiddenImportsFor(pkg), nil
}

// isRestrictedDir determines if the source directory has
// any restrictions placed on it by this configuration.
// A path will be restricted if: