presto-main/src/main/java/io/prestosql/server/security/JsonWebTokenAuthenticator.java/StaticKeyLoader/StaticKeyLoader
class StaticKeyLoader:        public StaticKeyLoader(String keyFile)
        {
            requireNonNull(keyFile, "keyFile is null");
            checkArgument(!keyFile.contains(KEY_ID_VARIABLE));
            this.key = loadKeyFile(new File(keyFile));
        }