protected Object doExecute(BackingEngine engine) throws Exception {
List<UserPrincipal> users = engine.listUsers();
ShellTable table = new ShellTable();
table.column("User Name");
table.column("Group");
table.column("Role");
for (UserPrincipal user : users) {
List<String> reportedRoles = new ArrayList<String>();
String userName = user.getName();