Here is a sample session:

 cheetah:~/comp/python/trunk>  ./python ./Lib/pdb.py hello
 > /home/ilya/comp/python/trunk/hello(1)<module>()
 -> print i
 (Pdb) b 1
 Breakpoint 1 at /home/ilya/comp/python/trunk/hello:1
 (Pdb) commands 1
 (com) 
 Traceback (most recent call last):
    self.cmdloop()
  File "/home/ilya/comp/python/trunk/Lib/cmd.py", line 142, in cmdloop
    stop = self.onecmd(line)
  File "/home/ilya/comp/python/trunk/Lib/pdb.py", line 273, in onecmd
    return cmd.Cmd.onecmd(self, line)
  File "/home/ilya/comp/python/trunk/Lib/cmd.py", line 219, in onecmd
    return func(arg)
  File "/home/ilya/comp/python/trunk/Lib/pdb.py", line 330, in    do_commands
    self.cmdloop()
  File "/home/ilya/comp/python/trunk/Lib/cmd.py", line 142, in cmdloop
    stop = self.onecm  File "/home/ilya/comp/python/trunk/Lib/bdb.py", line 66, in  dispatch_line
    self.user_line(frame)
  File "/home/ilya/comp/python/trunk/Lib/pdb.py", line 158, in user_line
    self.interaction(frame, None)
  File "/home/ilya/comp/python/trunk/Lib/pdb.py", line 206, in interaction
d(line)
  File "/home/ilya/comp/python/trunk/Lib/pdb.py", line 275, in onecmd
    return self.handle_command_def(line)
  File "/home/ilya/comp/python/trunk/Lib/pdb.py", line 293, in handle_command_def
    func = getattr(self, 'do_' + cmd)
 TypeError: cannot concatenate 'str' and 'NoneType' objects
 Uncaught exception. Entering post mortem debugging
 Running 'cont' or 'step' will restart the program
 > /home/ilya/comp/python/trunk/Lib/pdb.py(293)handle_command_def()
 -> func = getattr(self, 'do_' + cmd)