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 (!done) {
                LogPrintf("Adding fixed seed nodes as DNS doesn't seem to be available.\n");
                CNetAddr local;
                LookupHost("127.0.0.1", local, false);
                addrman.Add(convertSeed6(Params().FixedSeeds()), local);
                done = true;
            }
        }
        
        
        
        CAddress addrConnect;
        
        
        int nOutbound = 0;
        std::set<std::vector<unsigned char> > setConnected;
        {
            LOCK(cs_vNodes);
            BOOST_FOREACH(CNode* pnode, vNodes) {
                if (!pnode->fInbound) {
                    setConnected.insert(pnode->addr.GetGroup());
                    nOutbound++;
                }
            }
        }