Reported here https://github.com/bitcoin/bitcoin/pull/12629#issuecomment-381095603 by @Empact.  I've seen it now in a few different travis jobs, including:

https://travis-ci.org/bitcoin/bitcoin/jobs/366157920
https://travis-ci.org/bitcoin/bitcoin/jobs/366139851

From my initial investigation it seems like there may be an actual bug in block announcement, so I'm  opening this issue to track.
{
    
    bool needs_init = fReindex;
    if (!fReindex) {
        bool ret = LoadBlockIndexDB(chainparams);
        if (!ret) return false;
        needs_init = mapBlockIndex.empty();
    }
    if (needs_init) {
        
        
        
        
        
        LogPrintf("Initializing databases...\n");
        
        fTxIndex = gArgs.GetBoolArg("-txindex", DEFAULT_TXINDEX);
        pblocktree->WriteFlag("txindex", fTxIndex);
    }
    return true;
}
bool CChainState::LoadGenesisBlock(const CChainParams& chainparams)