https://travis-ci.org/github/bitcoin/bitcoin/jobs/679885530#L8791
CRPCCommand m_command;
    const CRPCCommand* m_wrapped_command;
};
class ChainImpl : public Chain
{
public:
    explicit ChainImpl(NodeContext& node) : m_node(node) {}
    Optional<int> getHeight() override
    {
        LOCK(::cs_main);
        const CChain& active = Assert(m_node.chainman)->ActiveChain();
        int height = active.Height();
        if (height >= 0) {
            return height;
        }
        return nullopt;
    }
    uint256 getBlockHash(int height) override
    {
        LOCK(::cs_main);
        const CChain& active = Assert(m_node.chainman)->ActiveChain();
        CBlockIndex* block = active[height];
        assert(block);
        return block->GetBlockHash();
    }
    bool haveBlockOnDisk(int height) override