The following will not stop for debugging:

    python3.8 -c 'import pdb; pdb.Pdb(skip=["__main__"]).set_trace()'

The example is contrived, the real case would be to have some "noisy" module being excluded in general, but when you add an explicit "set_trace()" in there it should still stop there, and not on some upper frame.

This was changed a long time already in https://github.com/python/cpython/commit/313a7513b0c5771042d850d70782a2448d1cdcb7 (Python 2.3), but it is not really clear.

I will create a PR reverting that part and see how it goes.