.DeleteRange([]byte("foo"), nil)   if n != 0 || rev != base+0 {    t.Errorf("#%d: n = %d, rev = %d, want (%d, %d)", i, n, rev, 0, base+0)   }    r, err = txn.Range([]byte("foo"), nil, RangeOptions{Rev: base + 0})   if err != nil {    t.