function onWrite( error ) {
		if ( error ) {
			debug( 'Encountered an error when writing bundle to file: %s', error.message );
			return done( error );
		}
		debug( 'Finished writing bundle `%s` to file.', b.name );
		if ( minify ) {
			return minifyBundle( tmp );
		}
		done();
	}
Callback invoked upon writing an un-minified bundle to file.

@private
@param {Error} [error] - error object
@returns {void}