Adding arbitrary logic to determine if PuDB stops

I'm building a solution for my team to run tests and debug them. Tests are run by pytest and PuDB is the debugger. I use `pytest-pudb` to launch pudb, but I want to switch from it because I want PuDB to pause not only on an exception, but I want it to pause immediately when Pytest reaches the first line of the test. (i.e. after it's done with all the Pytest bureaucracy.)

I'm thinking, how can I accomplish this? Now that PuDB is able to start paused ( #234 ) I'll be able to start PuDB, but I want it to stop on the first line of the test. Our test framework only runs one test in a single run. Currently the only solution I can think of is to programmatically figure out the code file and line number of the test, and then set a breakpoint there. But that is really cumbersome and fragile.

I wish PuDB had some way of letting me give it a condition. i.e. "next time you step into a file in the folder /foo/bar whose name starts with test_, pause, and then cancel this condition." Of course, this specific condition is tailor-made to my problem and it's very unlikely to be useful for others. But, maybe PuDB could accept arbitrary conditions? i.e. it'll have an API where I can give it a function, and then on every line it calls that function, and if it returns `True`, PuDB pauses, and if `False` it doesn't. Then anyone could put their complex logic in that function.

What do you think?