def METHOD_NAME():
    with open('configure.json') as configure_file:
        json_text = json.load(configure_file)
    source_dir = os.path.expanduser(json_text['FreeRTOS_source_dir'])
    thing_name = json_text['thing_name']
    # Read cert_pem from file
    cert_pem_filename = thing_name + '_cert_pem_file.pem'
    try:
        cert_pem_file = open(cert_pem_filename, 'r')
    except IOError:
        print("{} file not found. Run prerequisite step"
              .format(cert_pem_filename))
        sys.exit(1)
    else:
        cert_pem = cert_pem_file.read()
    # Read private_key_pem from file
    private_key_pem_filename = thing_name + '_private_key_pem_file.pem'
    try:
        private_key_pem_file = open(private_key_pem_filename, 'r')
    except IOError:
        print("{} file not found. Run prerequisite step"
              .format(private_key_pem_filename))
        sys.exit(1)
    else:
        private_key_pem = private_key_pem_file.read()
    # Modify 'demo_config.h' file
    misc.write_client_credentials(
        source_dir,
        thing_name=thing_name,
        client_certificate_pem=cert_pem,
        client_private_key_pem=private_key_pem,
        cleanup=False)