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 
{
    return FlatFileSeq(GetBlocksDir(), "rev", UNDOFILE_CHUNK_SIZE);
}
FILE* OpenBlockFile(const FlatFilePos &pos, bool fReadOnly) {
    return BlockFileSeq().Open(pos, fReadOnly);
}
static FILE* OpenUndoFile(const FlatFilePos &pos, bool fReadOnly) {
    return UndoFileSeq().Open(pos, fReadOnly);
}
fs::path GetBlockPosFilename(const FlatFilePos &pos)
{
    return BlockFileSeq().FileName(pos);
}
CBlockIndex * CChainState::InsertBlockIndex(const uint256& hash)
{
    AssertLockHeld(cs_main);
    if (hash.IsNull())
        return nullptr;
    
    BlockMap::iterator mi = mapBlockIndex.find(hash);
    if (mi != mapBlockIndex.end())
        return (*mi).second;
    
    CBlockIndex* pindexNew = new CBlockIndex();
    mi = mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
    pindexNew->phashBlock = &((*mi).first);
    return pindexNew;
}
bool CChainState::LoadBlockIndex(const Consensus::Params& consensus_params, CBlockTreeDB& blocktree)