Debug mode

According to odoo.py --help

--debug             enable debug mode

so start odoo with

odoo.py --debug

PDB

You have to edit the python file you want to debug by adding a breakpoint with

import pdb

pdb.set_trace()

and start odoo normally.

import pdb

whitch line in to breackpoint (debug mode start) you want, before Add this line  pdb.set_trace()

• In terminal side 

"S"  for Next step

Execute the current line, stop at the first possible occasion (either in a function that is called or on the next line in the current function).

"N" for next line

Continue execution until the next line in the current function is reached or it returns. (The difference between next and step is that step stops inside a called function, while next executes called functions at (nearly) full speed, only stopping at the next line in the current function.)