2to3 translation problem

[Tony van der Hoff]

Debian Jessie, python 2.7; python 3.4

I have an application, using pygame for graphics, that works fine under 
python2.7. I have run it through 2to3, but when running the result under 
python 3.4, I get the error :

Traceback (most recent call last):
   File "ppm304.py", line 9, in <module>
     import pygame
ImportError: No module named 'pygame'

So, python 3.4 can't find the library, whilst python 2.7 can.
How do I track down/fix the missing dependency.