When an exception is raised in my callback, I simply see a message like this one:

Exception TypeError: "argument of type 'NoneType' is not iterable" in 'netfilterqueue.global_callback' ignored

This makes troubleshooting painful. Is there a safe way for you to allow the exception to terminate the script with the normal stack trace? Short of that, maybe a constructor argument or other mutator to give developers the ability to opt for more detailed exception information?

I'd like to be more helpful but at a glance I can't tell where these exceptions are being handled and silenced. If you can point me to it, I'll be happy to take a crack at a PR.