Activation Fails on include base_class.object.php

Activation of WordPress Development Kit Plugin fails:

PHP Fatal error: require_once(): Failed opening required ‘base_class.object.php’
in … wp-content\plugins\wp-dev-kit\include\class.wpdk.php on line 82

This is in the constructor:

 function __construct() {
        $this->url = plugins_url( '', WPDK__PLUGIN_FILE );
        $this->dir = WPDK__PLUGIN_DIR;
        $this->slug = plugin_basename( WPDK__PLUGIN_FILE );

        require_once( 'base_class.object.php' );

        add_action( 'admin_menu', array( $this, 'admin_menu' ) );
        add_action( 'wp_enqueue_scripts', array( $this, 'createobject_UI' ) );
        add_action( 'rest_api_init', array( $this, 'load_rest_handler' ) );
    }