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(request.params[1].isNum())
            verbosity = request.params[1].get_int();
        else
            verbosity = request.params[1].get_bool() ? 1 : 0;
    }
    const CBlockIndex* pblockindex = LookupBlockIndex(hash);
    if (!pblockindex) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
    }
    const CBlock block = GetBlockChecked(pblockindex);
    if (verbosity <= 0)
    {
        CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
        ssBlock << block;
        std::string strHex = HexStr(ssBlock.begin(), ssBlock.end());
        return strHex;
    }
    return blockToJSON(block, chainActive.Tip(), pblockindex, verbosity >= 2);
}
struct CCoinsStats
{
    int nHeight;
    uint256 hashBlock;
    uint64_t nTransactions;
    uint64_t nTransactionOutputs;
    uint64_t nBogoSize;
    uint256 hashSerialized;
    uint64_t nDiskSize;
    CAmount nTotalAmount;
    CCoinsStats() : nHeight(0), nTransactions(0), nTransactionOutputs(0), nBogoSize(0), nDiskSize(0), nTotalAmount(0) {}