gdb breakpoint in python module

[Viesturs]

I import a custom made python library

from Jets.Analysis.Plot import *

I would like to set a gdb breakpoint in the module source file Plot.py

The python executable is wrapped by a shell executable shexec.sh

I proceed as follows:

gdb
file sh
break path_to_module/Plot.py:299
run shexec.sh arg1 arg2

The breakpoint is entirely ignored.

What is wrong?