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 
{
    UniValue result(UniValue::VOBJ);
    result.pushKV("hash", blockindex->GetBlockHash().GetHex());
    const CBlockIndex* pnext;
    int confirmations = ComputeNextBlockAndDepth(tip, blockindex, pnext);
    result.pushKV("confirmations", confirmations);
    result.pushKV("strippedsize", (int)::GetSerializeSize(block, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS));
    result.pushKV("size", (int)::GetSerializeSize(block, PROTOCOL_VERSION));
    result.pushKV("weight", (int)::GetBlockWeight(block));
    result.pushKV("height", blockindex->nHeight);
    result.pushKV("version", block.nVersion);
    result.pushKV("versionHex", strprintf("%08x", block.nVersion));
    result.pushKV("merkleroot", block.hashMerkleRoot.GetHex());
    UniValue txs(UniValue::VARR);
    for(const auto& tx : block.vtx)
    {
        if(txDetails)
        {
            UniValue objTx(UniValue::VOBJ);
            TxToUniv(*tx, uint256(), objTx, true, RPCSerializationFlags());
            txs.push_back(objTx);
        }
        else
            txs.push_back(tx->GetHash().GetHex());
    }
    result.pushKV("tx", txs);
    result.pushKV("time", block.GetBlockTime());
    result.pushKV("mediantime", (int64_t)blockindex->GetMedianTimePast());