Current bitcoin-master on testnet, `maxconnections=8` in the config file. Running in VM that doesn't have public IP and is not reachable from the Internet.

Wait until you have 8 peers.

```
telnet localhost 18333
```

It will result in:

```
Assertion failed: (nMaxInbound > 0), function AcceptConnection, file net.cpp, line 973.
```

First found in https://github.com/bitcoin/bitcoin/pull/8996, but can be reproduced on master.

{
            LOCK(cs_vNodes);
            vNodes.push_back(pnode);
        }
        pnode->nServicesExpected = ServiceFlags(addrConnect.nServices & nRelevantServices);
        pnode->nTimeConnected = GetTime();
        return pnode;
    } else if (!proxyConnectionFailed) {
        
        
        addrman.Attempt(addrConnect, fCountFailure);
    }
    return NULL;
}
void CConnman::DumpBanlist()
{
    SweepBanned(); 
    if (!BannedSetIsDirty())
        return;
    int64_t nStart = GetTimeMillis();
    CBanDB bandb;
    banmap_t banmap;
    SetBannedSetDirty(false);
    GetBanned(banmap);
    if (!bandb.Write(banmap))
        SetBannedSetDirty(true);
    LogPrint("net", "Flushed %d banned node ips/subnets to banlist.dat  %dms\n",
        banmap.size(), GetTimeMillis() - nStart);
}
void CNode::CloseSocketDisconnect()