pdb for setuptools console scripts

A console script installed by setuptools is a thin wrapper that loads the defined entry point and invokes it. pdbcs uses the console script name to load the entry point itself and invoke the debugger. The debugger automatically stops on the first line of the main function of the console script.

$ pdbcs /Users/dhellmann/Envs/pdbcs/bin/pdbcs
> /Users/dhellmann/Devel/pdbcs/pdbcs/pdbcs/main.py(11)main()
-> parser = argparse.ArgumentParser()
(Pdb)