I tried using the exec command to run the python script from within my shell script, but then received errors about not recognizing the run_or_die('svn up') command.

Not to worry. I saw enough in your script to derive the following in my build script:

SVN_VERSION="`head -n4 ./src/.svn/entries | tail -n1`"

I will use that variable as part of the package name. For example:

kdelibs-3.5.11-i486-svn_1167630.tgz.

I will have to watch your release announcements to know when to update 3.5.11 to 3.5.12.

Is that major version number cleverly hidden somewhere in the svn tree?