svoid drainErrorStreamToConsole(InputStream errorStream, IPred<S> printIf, Runnable enter) {
  thread {
    callF(enter);
    DataInputStream err = new(errorStream);
    S line;
    while ping ((line = err.readLine()) != null) {
      if (printIf == null || printIf.get(line))
        print("ERR: " + line);
    }
  }
}