presto-client/src/main/java/io/prestosql/client/KerberosUtil.java/KerberosUtil/defaultCredentialCachePath
class KerberosUtil:    public static Optional<String> defaultCredentialCachePath()
    {
        String value = nullToEmpty(System.getenv("KRB5CCNAME"));
        if (value.startsWith(FILE_PREFIX)) {
            value = value.substring(FILE_PREFIX.length());
        }
        return Optional.ofNullable(emptyToNull(value));
    }