Reported here: https://github.com/bitcoin/bitcoin/pull/10244#issuecomment-378035305

Travis log here: https://travis-ci.org/bitcoin/bitcoin/jobs/361243719#L2810

Note the JSON exception:

```
test_framework.authproxy.JSONRPCException: The mempool was not loaded yet (-1) 
```

That exception was introduced here: https://github.com/bitcoin/bitcoin/commit/cb1e319fe9e198c9c5cf5236fe9af5a3d748b9e8#diff-a0c8f511d90e83aa9b5857e819ced344R1617

cc @jtimon 
{
    setEntries parentIters = GetMemPoolParents(it);
    
    for (txiter piter : parentIters) {
        UpdateChild(piter, it, add);
    }
    const int64_t updateCount = (add ? 1 : -1);
    const int64_t updateSize = updateCount * it->GetTxSize();
    const CAmount updateFee = updateCount * it->GetModifiedFee();
    for (txiter ancestorIt : setAncestors) {
        mapTx.modify(ancestorIt, update_descendant_state(updateSize, updateFee, updateCount));
    }
}
void CTxMemPool::UpdateEntryForAncestors(txiter it, const setEntries &setAncestors)