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 
const CBlockIndex* block = tip;
        assert(block);
        while (block->pprev && (block->pprev->nStatus & BLOCK_HAVE_DATA)) {
            block = block->pprev;
        }
        obj.pushKV("pruneheight",        block->nHeight);
        
        bool automatic_pruning = (gArgs.GetArg("-prune", 0) != 1);
        obj.pushKV("automatic_pruning",  automatic_pruning);
        if (automatic_pruning) {
            obj.pushKV("prune_target_size",  nPruneTarget);
        }
    }
    const Consensus::Params& consensusParams = Params().GetConsensus();
    UniValue softforks(UniValue::VARR);
    UniValue bip9_softforks(UniValue::VOBJ);
    softforks.push_back(SoftForkDesc("bip34", 2, tip, consensusParams));
    softforks.push_back(SoftForkDesc("bip66", 3, tip, consensusParams));
    softforks.push_back(SoftForkDesc("bip65", 4, tip, consensusParams));
    for (int pos = Consensus::DEPLOYMENT_CSV; pos != Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++pos) {
        BIP9SoftForkDescPushBack(bip9_softforks, consensusParams, static_cast<Consensus::DeploymentPos>(pos));
    }
    obj.pushKV("softforks",             softforks);
    obj.pushKV("bip9_softforks", bip9_softforks);
    obj.pushKV("warnings", GetWarnings("statusbar"));
    return obj;
}
struct CompareBlocksByHeight
{
    bool operator()(const CBlockIndex* a, const CBlockIndex* b) const