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.fHelp || request.params.size() != 0)
        throw std::runtime_error(
            RPCHelpMan{"getmempoolinfo",
                "\nReturns details on the active state of the TX memory pool.\n",
                {},
                RPCResult{
            "{\n"
            "  \"loaded\": true|false         (boolean) True if the mempool is fully loaded\n"
            "  \"size\": xxxxx,               (numeric) Current tx count\n"
            "  \"bytes\": xxxxx,              (numeric) Sum of all virtual transaction sizes as defined in BIP 141. Differs from actual serialized size because witness data is discounted\n"
            "  \"usage\": xxxxx,              (numeric) Total memory usage for the mempool\n"
            "  \"maxmempool\": xxxxx,         (numeric) Maximum memory usage for the mempool\n"
            "  \"mempoolminfee\": xxxxx       (numeric) Minimum fee rate in " + CURRENCY_UNIT + "/kB for tx to be accepted. Is the maximum of minrelaytxfee and minimum mempool fee\n"
            "  \"minrelaytxfee\": xxxxx       (numeric) Current minimum relay fee for transactions\n"
            "}\n"
                },
                RPCExamples{
                    HelpExampleCli("getmempoolinfo", "")
            + HelpExampleRpc("getmempoolinfo", "")
                },
            }.ToString());
    return MempoolInfoToJSON(::mempool);
}
static UniValue preciousblock(const JSONRPCRequest& request)