The workaround could be
...
InitialContext ctx = new InitialContext();
DataSource datasource = (javax.sql.DataSource) ctx.lookup ("java:/comp/env/jdbc/DS");
Map<String, Object> props = new HashMap<String, Object>();
props.put(Environment.DATASOURCE, dataSource);
EntityManagerFactory emf = Persistence.createEntityManagerFactory(UNIT_NAME, props);
...