I downloaded python 2.6 here, extracted the zip file and copied FolderExtracted//Python-2.6.9/Mac/Resources/framework/Info.plist.in to /Applications/XBMC.app/Contents/Frameworks/lib/python2.6/. I renamed the file from Info.plist.in to Info.plist and ran the self-sign code mentioned earlier in this thread.
codesign -s "Certificate Name" -f --deep /Applications/XBMC.app/
This succeeded without problems and validating showed the app was signed.
codesign -vvv /Applications/XBMC.app/
/Applications/XBMC.app/: valid on disk
/Applications/XBMC.app/: satisfies its Designated Requirement