check.go
func (c *Check) Unknownf(format string, v ...interface{}) {
	c.Exitf(UNKNOWN, format, v...)
}
func (c *Check) Unknownf(format string, v ...interface{}) {
	c.Exitf(UNKNOWN, format, v...)
}
// Unknownf is a shorthand function which exits the check with status
// UNKNOWN and the message provided.