OK, and how is it any surprise at all? What you need is to package those dependencies, too. Why would you expect it to be any different way?
> What do the gurus in Debian say about this?
> * Suppose your Python package has 10 dependencies that are not in the Debian official repository. In this case, you are suggested to package these 10 Python libraries first, submit them to the Debian official repository and then package your own app.
> * If you are feeling too lazy [...] you are then suggested to refactor your code so that you only depend on the Python standard libraries and nothing else.
And what is wrong with these approaches?
Also, if you rely on ten libraries in your trivial application, you worked very hard for this outcome. pip, Ruby gems, and NPM make incorporating unnecessary dependencies too easy as they are at this point. Recall the left-pad farce.
I am a sysadmin who also writes code, so I have seen the landscape from both sides. I take the packaging into an account before I write my first line. I try to keep dependencies reasonably small. All this because I've seen what it takes to maintain packages for a Linux distribution. And now we have you whining that Debian doesn't make their life hard to fullfil your ridiculous expectations as a random petty programmer.