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.

{
    if (CNode* pnode = FindNode(subNet)) {
        pnode->fDisconnect = true;
        return true;
    }
    return false;
}
bool CConnman::DisconnectNode(const std::string& strNode)
{
    if (CNode* pnode = FindNode(strNode)) {
        pnode->fDisconnect = true;
        return true;
    }
    return false;
}
bool CConnman::DisconnectNode(NodeId id)
{
    LOCK(cs_vNodes);
    for(CNode* pnode : vNodes) {
        if (id == pnode->id) {
            pnode->fDisconnect = true;
            return true;
        }
    }
    return false;
}
void CConnman::RelayTransaction(const CTransaction& tx)