theme_M2-Venus_Fasony/app/design/frontend/Venustheme/fasony/registration.php

<?php
/**
* Copyright © 2015 Magento. All rights reserved.
* See COPYING.txt for license details.
*/
\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::THEME,
    'frontend/Venustheme/fasony',
    __DIR__
);