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 
}
            if (ShutdownRequested())
                return false;
        }
        std::map<uint256, CAmount> mapDeltas;
        file >> mapDeltas;
        for (const auto& i : mapDeltas) {
            mempool.PrioritiseTransaction(i.first, i.second);
        }
    } catch (const std::exception& e) {
        LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing anyway.\n", e.what());
        return false;
    }
    LogPrintf("Imported mempool transactions from disk: %i succeeded, %i failed, %i expired, %i already there\n", count, failed, expired, already_there);
    return true;
}
bool DumpMempool()
{
    int64_t start = GetTimeMicros();
    std::map<uint256, CAmount> mapDeltas;
    std::vector<TxMempoolInfo> vinfo;
    static Mutex dump_mutex;
    LOCK(dump_mutex);
    {
        LOCK(mempool.cs);
        for (const auto &i : mempool.mapDeltas) {
            mapDeltas[i.first] = i.second;
        }
        vinfo = mempool.infoAll();
    }