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 
if (fs::exists(config_file_path)) {
        LogPrintf("Config file: %s\n", config_file_path.string());
    } else if (gArgs.IsArgSet("-conf")) {
        
        InitWarning(strprintf(_("The specified config file %s does not exist\n"), config_file_path.string()));
    } else {
        
        LogPrintf("Config file: %s (not found, skipping)\n", config_file_path.string());
    }
    LogPrintf("Using at most %i automatic connections (%i file descriptors available)\n", nMaxConnections, nFD);
    
    if (gArgs.IsArgSet("-datadir") && !fs::path(gArgs.GetArg("-datadir", "")).is_absolute()) {
        LogPrintf("Warning: relative datadir option '%s' specified, which will be interpreted relative to the " 
                  "current working directory '%s'. This is fragile, because if bitcoin is started in the future "
                  "from a different location, it will be unable to locate the current data files. There could "
                  "also be data loss if bitcoin is started while in a temporary directory.\n",
            gArgs.GetArg("-datadir", ""), fs::current_path().string());
    }
    InitSignatureCache();
    InitScriptExecutionCache();
    LogPrintf("Using %u threads for script verification\n", nScriptCheckThreads);
    if (nScriptCheckThreads) {
        for (int i=0; i<nScriptCheckThreads-1; i++)
            threadGroup.create_thread(&ThreadScriptCheck);
    }
    
    CScheduler::Function serviceLoop = std::bind(&CScheduler::serviceQueue, &scheduler);
    threadGroup.create_thread(std::bind(&TraceThread<CScheduler::Function>, "scheduler", serviceLoop));
    GetMainSignals().RegisterBackgroundSignalScheduler(scheduler);
    GetMainSignals().RegisterWithMempoolSignals(mempool);