Sure, that's beautiful in theory. But you have to remember to catch the strings "import pdb", "import ipdb", "import pydbgr", and the variations "from pdb import Pdb", "__import__('pdb')", all the permutations, and so on. Anyway, that's besides point.
Having to change the source to fire the debugger is a dumb way of debugging after all, and doesn't allow certain things (e.g., step thru a 3rd party library). Better coach the developers on how to use the tools properly.
I agree that this method is much better, and for some reason reminds me of the tooling vs programming languages discussion I was in the other day.
I guess it's because that is an example of ad-hoc (which typically misses a lot of edge conditions) tooling created to make up for language (or in this case tooling) inadequacies.
Having to change the source to fire the debugger is a dumb way of debugging after all, and doesn't allow certain things (e.g., step thru a 3rd party library). Better coach the developers on how to use the tools properly.