cmd/stellar-vanity-gen/main.go
func checkPlausible() {
	for _, r := range prefix {
		if !strings.ContainsRune(alphabet, r) {
			fmt.Printf("Invalid prefix: %s is not in the base32 alphabet\n", strconv.QuoteRune(r))
			os.Exit(1)
		}
	}
}
func checkPlausible() {
	for _, r := range prefix {
		if !strings.ContainsRune(alphabet, r) {
			fmt.Printf("Invalid prefix: %s is not in the base32 alphabet\n", strconv.QuoteRune(r))
			os.Exit(1)
		}
	}
}
// aborts the attempt if a desired character is not a valid base32 digit