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 (scores.empty()) {
        return;
    }
    std::sort(scores.begin(), scores.end());
    
    const double weights[NUM_GETBLOCKSTATS_PERCENTILES] = {
        total_weight / 10.0, total_weight / 4.0, total_weight / 2.0, (total_weight * 3.0) / 4.0, (total_weight * 9.0) / 10.0
    };
    int64_t next_percentile_index = 0;
    int64_t cumulative_weight = 0;
    for (const auto& element : scores) {
        cumulative_weight += element.second;
        while (next_percentile_index < NUM_GETBLOCKSTATS_PERCENTILES && cumulative_weight >= weights[next_percentile_index]) {
            result[next_percentile_index] = element.first;
            ++next_percentile_index;
        }
    }
    
    for (int64_t i = next_percentile_index; i < NUM_GETBLOCKSTATS_PERCENTILES; i++) {
        result[i] = scores.back().first;
    }
}
template<typename T>
static inline bool SetHasKeys(const std::set<T>& set) {return false;}