Force a specific version of a framework for a process
A dangerous way to move forward is to use the DYLD_INSERT_LIBRARIES environment variable to change which python framework the calendar server uses. You will need to edit the launchd plist for the calendar server inside of the Server.app bundle to add your the environment variable. Look in Server.app/Contents/ServerRoot/System/Library/LaunchDaemons/  for the file.
The man pages for launchd.plist(5) and dyld(1) will be useful. Also the otool -L command may help you track down dependancies.
I'm not sure how well the calendar server will run with these changes.