func (c *Check) AddResultf(status Status, format string, v ...interface{}) {
	msg := fmt.Sprintf(format, v...)
	c.AddResult(status, msg)
}
func (c *Check) AddResultf(status Status, format string, v ...interface{}) {
	msg := fmt.Sprintf(format, v...)
	c.AddResult(status, msg)
}
// AddResultf functions as AddResult, but takes a printf-style format
// string and arguments.