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 
return a->GetTx().GetHash() < b->GetTx().GetHash();
        }
    };
    typedef std::set<txiter, CompareIteratorByHash> setEntries;
    const setEntries & GetMemPoolParents(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
    const setEntries & GetMemPoolChildren(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
    uint64_t CalculateDescendantMaximum(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
private:
    typedef std::map<txiter, setEntries, CompareIteratorByHash> cacheMap;
    struct TxLinks {
        setEntries parents;
        setEntries children;
    };
    typedef std::map<txiter, TxLinks, CompareIteratorByHash> txlinksMap;
    txlinksMap mapLinks;
    void UpdateParent(txiter entry, txiter parent, bool add);
    void UpdateChild(txiter entry, txiter child, bool add);
    std::vector<indexed_transaction_set::const_iterator> GetSortedDepthAndScore() const EXCLUSIVE_LOCKS_REQUIRED(cs);
public:
    indirectmap<COutPoint, const CTransaction*> mapNextTx GUARDED_BY(cs);
    std::map<uint256, CAmount> mapDeltas;
    /** Create a new CTxMemPool.
     */
    explicit CTxMemPool(CBlockPolicyEstimator* estimator = nullptr);
    /**
     * If sanity-checking is turned on, check makes sure the pool is
     * consistent (does not contain two transactions that spend the same inputs,
     * all inputs are in the mapNextTx array). If sanity-checking is turned off,
     * check does nothing.
     */