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 
g_wallet_init_interface.Construct(interfaces);
    /* Register RPC commands regardless of -server setting so they will be
     * available in the GUI RPC console even if external calls are disabled.
     */
    RegisterAllCoreRPCCommands(tableRPC);
    for (const auto& client : interfaces.chain_clients) {
        client->registerRpcs();
    }
    g_rpc_interfaces = &interfaces;
#if ENABLE_ZMQ
    RegisterZMQRPCCommands(tableRPC);
#endif
    /* Start the RPC server already.  It will be started in "warmup" mode
     * and not really process calls already (but it will signify connections
     * that the server is there and will be ready later).  Warmup mode will
     * be disabled when initialisation is finished.
     */
    if (gArgs.GetBoolArg("-server", false))
    {
        uiInterface.InitMessage_connect(SetRPCWarmupStatus);
        if (!AppInitServers())
            return InitError(_("Unable to start HTTP server. See debug log for details."));
    }
    
    for (const auto& client : interfaces.chain_clients) {
        if (!client->verify()) {