Add 'make before-push' target.
Stop using more deprecated test methods.
Use for loop instead of map.
NEWS entry for python3 changes.
Check for bytes rather than str.
Use bytes literals instead of string literals.
Use six.moves.
Apply libmodernize.fixes.fix_dict.

(Exclude dulwich.objects)
Use six.byte2int, .indexbytes, and .iterbytes.
Fix PackBasedObjectStore.packs.
String stuff (It's late.)
stuff