[CentOS] ananconda update.img creation fails: generated but with wrong python version in /usr/sbin/anaconda contained

Hi all,
I've created an anaconda update.img file per instructions at https://fedoraproject.org/wiki/Anaconda/Updates for Centos 7.2. The problem is that the update.img file contains references to python3 (say, file /usr/sbin/anaconda), and so the all installation fails immediately. My question is: what are the steps to create an anaconda update image appropriate for a particular centos release? Thanks a lot.

The steps I have performed (to create an update.img) are listed below:

 1) find the version of ananconda that centos 7.2 installation media: 21.48.22.56-1.
 2) follow the instructions at the above wiki page, and wiki https://fedoraproject.org/wiki/Anaconda. Run the following command (to generate update.img):
 2.1 yum -y install git 2.2 git clone https://fedoraproject.org/wiki/Anaconda 
 2.3 cd anaconda 2.4 scripts/makeupdates -t anaconda-21.48.22.56-1
3) save the generated image to place under .../images directory.
>From what I see, all PXE clients did download the new update.img file and merge the changes contained. But because the updated anaconda pointed to python3 instead of python 2.7.5 (the version comes with installation media), the installation process failed immediately.
Thanks.
Best,David