Use 2to3 in setup.py.
Alter itertools import statement so that 2to3 fixes it.
Use byte literal in test_pack.py so that module can be imported in py3.
web: don't echo back invalid service names

This prevents potential XSS attacks, which could have injected
arbitrary content under a domain by echoing back the unsupported
service name.
Merge branch 'service-name-xss' of git://github.com/durin42/dulwich
Add test for echoing back service name in dulwich.web invalid service reply.