Fortunately, macports has updated their Subversion port to 1.7.0, so I could test the issue. There's indeed a change in svn.repos.ChangeCollector.delete_entry(), where the construction of ChangedPath now takes a non-Nonepath argument. This seems like a pretty arbitrary change, and I'm a bit worried there may be other "vicious" issues like this popping up.
Anyway, your fix is almost correct, except for the fact that change.action was only introduced in 1.5.0, and AFAIK we still support 1.3 and 1.4. The complete fix is in , and passes all tests with Subversion 1.6.17 and 1.7.0 (I don't have older versions, unfortunately).