pypy2

[RamKromberg]

I tried running pdfsizeopt with pypy2 but __cmp__ isn't available. Porting requires re-implementing the relevant methods (only 3-4 one liners I believe) with rich comparisons but since I don't actually understand the underlying logic behind the castings, I can't do it. Seeing how you're be more familiar with the code base and python, I figured you might want to have a crack at it.

REF: https://portingguide.readthedocs.io/en/latest/comparisons.html

Anyhow, I'm not sure it's the only problem or whether pypy2 maintenance will continue (currently they're back-porting some features here and there but mostly just security fixes), but this one seems to overlap with python3 changes to python2 anyhow so it will need to be sorted out for any future porting attempts regardless so it should be a viable first step at least.