mkinitrd (/usr/libexec/mkliveinitrd) uses only isomd5sum binary. isomd5sum package depends on python which is not needed in this case. There's no point to pull python package to minimal installs (consider special installations like lightweight virtual guests). I propose to move /usr/lib/python2.6/site-packages/pyisomd5sum.so to the -python subpacakge and modify dependencies according to that.
Done for rawhide (well, removed the python module altogether since nothing is using it)