WP_REST_Plugins_Controller::is_filesystem_available(): true|WP_Error

853	protected function is_filesystem_available() {854		$filesystem_method = get_filesystem_method();855 856		if ( 'direct' === $filesystem_method ) {857			return true;858		}859 860		ob_start();861		$filesystem_credentials_are_stored = request_filesystem_credentials( self_admin_url() );862		ob_end_clean();863 864		if ( $filesystem_credentials_are_stored ) {865			return true;866		}867 868		return new WP_Error( 'fs_unavailable', __( 'The filesystem is currently unavailable for managing plugins.' ), array( 'status' => 500 ) );869	}