code: func Validate(spec SysSpec, validators []Validator) (error, error) {
  	var errs []error
  	var warns []error
  
  	for _, v := range validators {
  		fmt.Printf("Validating %s...\n", v.Name())
  		warn, err := v.Validate(spec)
  		errs = append(errs, err)
  		warns = append(warns, warn)
  	}
  	return errorsutil.NewAggregate(warns), errorsutil.NewAggregate(errs)
  }
docs: // Validate uses validators to validate the system and returns a warning or error.