I know exactly what you're problem is. (I had the same issue, and used strace to find the problem.)
Here's the solution:
After you're done installing subversion, you need to make the libraries available from the location referenced. (libsvn and svn)
In my installation, these are the exact commands that I executed to fix this:
ln -s ~/packages/lib/svn-python/libsvn
ln -s ~/packages/lib/svn-python/svn
This is taken from my guide at http://natmaster.com/articles/installing_trac.php so you can probably figure out what's best for your setup based on the information there.
Ask me if you need any more help!