Steps to invoke PDB to debug python scripts

Actually this is the replica of https://stackoverflow.com/questions/35496298/pdb-automatically-append-to-sys-path

Probably it is tedious, but at least it works:

1. switch from python [my-script] to python -m pdb [my-script].
2. import sys
3. sys.path.append([full path to subdirectory where [module-XY] lies])
4. b [module-XY]:[line]