Python – SVN serve and PySVN Error message: Expected FS format between ‘1’ and ‘3’; found format ‘4’

For research purposes, I copied a SVN repo to my Windows machine using svnsync so I can replay on my machine without loading the actual server.

I've been using PySVN in scripts to control the revision number I want the repo to be in and have been using it fine so far. Now I got a repo from a different project and svnsync got it fine. When I try to run the script in Ubuntu I get:
Expected FS format between '1' and '3'; found format '4'

From what I was able to learn from other questions on StackOverFlow and elsewhere, it seems that my ubuntu pysvn is out of date for a 1.6 subversion version and would only work for 1.5. Did I understand this correctly?

Because on the pysvn download page it says that "This release of pysvn has been tested against Subversion 1.5.6 and Subversion 1.6.5"

When I do sudo apt-get install python-svn it tells me that python-svn is already the newest version. So I'm assuming that PySVN doesn't support 1.6 Subversion repos.

But if I try running the exact same script on a Windows box, with only pysvn module on it (no svn installation), and the local repo files, it runs fine and I can checkout files!

So I'm confused. Why does PySVN run with FS format 4 repos on windows and not on Ubuntu?