Source

File: wp-includes/class-wp-customize-manager.php

public function prepare_setting_validity_for_js( $validity ) {
		if ( is_wp_error( $validity ) ) {
			$notification = array();
			foreach ( $validity->errors as $error_code => $error_messages ) {
				$notification[ $error_code ] = array(
					'message' => join( ' ', $error_messages ),
					'data'    => $validity->get_error_data( $error_code ),
				);
			}
			return $notification;
		} else {
			return true;
		}
	}