How to use the es6-promise/lib/es6-promise/promise.js.reject function in es6-promise

export function rollup ( options ) {
	if ( !options || !options.entry ) {
		return Promise.reject( new Error( 'You must supply options.entry to rollup' ) );
	}

	if ( options.transform || options.load || options.resolveId || options.resolveExternal ) {
		return Promise.reject( new Error( 'The `transform`, `load`, `resolveId` and `resolveExternal` options are deprecated in favour of a unified plugin API. See https://github.com/rollup/rollup/wiki/Plugins for details' ) );
	}

	const error = validateKeys( options, ALLOWED_KEYS );

	if ( error ) {
		return Promise.reject( error );
	}

	const bundle = new Bundle( options );

	return bundle.build().then( () => {
		return {
			imports: bundle.externalModules.map( module => module.id ),
			exports: keys( bundle.entryModule.exports ),
			modules: bundle.orderedModules.map( module => {
				return { id: module.id };

export function rollup ( options ) {
	if ( !options || !options.entry ) {
		return Promise.reject( new Error( 'You must supply options.entry to rollup' ) );
	}

	if ( options.transform || options.load || options.resolveId || options.resolveExternal ) {
		return Promise.reject( new Error( 'The `transform`, `load`, `resolveId` and `resolveExternal` options are deprecated in favour of a unified plugin API. See https://github.com/rollup/rollup/wiki/Plugins for details' ) );
	}

	const error = validateKeys( options, ALLOWED_KEYS );

	if ( error ) {
		return Promise.reject( error );
	}

	const bundle = new Bundle( options );

	return bundle.build().then( () => {
		return {
			imports: bundle.externalModules.map( module => module.id ),
			exports: keys( bundle.entryModule.exports ),
			modules: bundle.orderedModules.map( module => {
				return { id: module.id };
			}),

			generate: options => bundle.render( options ),
			write: options => {
				if ( !options || !options.dest ) {
					throw new Error( 'You must supply options.dest to bundle.write' );