It isn't find the source tarball, which isn't surprising since that version is very old (py-pythoncad was updated to DS1-R22 over 4.5 years ago). The reason for python24 is anything py-* prefixed wants 2.4, py25-* 2.5, py26-* 2.6 etc.
Probably the best thing would be for someone to make a python 2.6 version of this port and update it to the current release of pythoncad...however, since this port is unmaintained and I don't see any other tickets, you may be the first to have tried it in quite a while.
