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 
{ "blockchain",         "getblockhash",           &getblockhash,           {"height"} },
    { "blockchain",         "getblockheader",         &getblockheader,         {"blockhash","verbose"} },
    { "blockchain",         "getchaintips",           &getchaintips,           {} },
    { "blockchain",         "getdifficulty",          &getdifficulty,          {} },
    { "blockchain",         "getmempoolancestors",    &getmempoolancestors,    {"txid","verbose"} },
    { "blockchain",         "getmempooldescendants",  &getmempooldescendants,  {"txid","verbose"} },
    { "blockchain",         "getmempoolentry",        &getmempoolentry,        {"txid"} },
    { "blockchain",         "getmempoolinfo",         &getmempoolinfo,         {} },
    { "blockchain",         "getrawmempool",          &getrawmempool,          {"verbose"} },
    { "blockchain",         "gettxout",               &gettxout,               {"txid","n","include_mempool"} },
    { "blockchain",         "gettxoutsetinfo",        &gettxoutsetinfo,        {} },
    { "blockchain",         "pruneblockchain",        &pruneblockchain,        {"height"} },
    { "blockchain",         "savemempool",            &savemempool,            {} },
    { "blockchain",         "verifychain",            &verifychain,            {"checklevel","nblocks"} },
    { "blockchain",         "preciousblock",          &preciousblock,          {"blockhash"} },
    { "blockchain",         "scantxoutset",           &scantxoutset,           {"action", "scanobjects"} },
    
    { "hidden",             "invalidateblock",        &invalidateblock,        {"blockhash"} },
    { "hidden",             "reconsiderblock",        &reconsiderblock,        {"blockhash"} },
    { "hidden",             "waitfornewblock",        &waitfornewblock,        {"timeout"} },
    { "hidden",             "waitforblock",           &waitforblock,           {"blockhash","timeout"} },
    { "hidden",             "waitforblockheight",     &waitforblockheight,     {"height","timeout"} },
    { "hidden",             "syncwithvalidationinterfacequeue", &syncwithvalidationinterfacequeue, {} },
};
void RegisterBlockchainRPCCommands(CRPCTable &t)
{
    for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
        t.appendCommand(commands[vcidx].name, &commands[vcidx]);
}