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 
int64_t swtxs = 0;
    int64_t total_size = 0;
    int64_t total_weight = 0;
    int64_t utxo_size_inc = 0;
    std::vector<CAmount> fee_array;
    std::vector<std::pair<CAmount, int64_t>> feerate_array;
    std::vector<int64_t> txsize_array;
    for (const auto& tx : block.vtx) {
        outputs += tx->vout.size();
        CAmount tx_total_out = 0;
        if (loop_outputs) {
            for (const CTxOut& out : tx->vout) {
                tx_total_out += out.nValue;
                utxo_size_inc += GetSerializeSize(out, PROTOCOL_VERSION) + PER_UTXO_OVERHEAD;
            }
        }
        if (tx->IsCoinBase()) {
            continue;
        }
        inputs += tx->vin.size(); 
        total_out += tx_total_out; 
        int64_t tx_size = 0;
        if (do_calculate_size) {
            tx_size = tx->GetTotalSize();
            if (do_mediantxsize) {
                txsize_array.push_back(tx_size);
            }
            maxtxsize = std::max(maxtxsize, tx_size);
            mintxsize = std::min(mintxsize, tx_size);
            total_size += tx_size;