Red Hat Virtualization Hypervisor installation fails with a missing YUM package group "core"

Issue

• I followed https://access.redhat.com/documentation/en-us/red_hat_virtualization/4.1/html/installation_guide/advanced_rhvh_install, but it failed with "no suitable image" error before anaconda starts.
• I modified to use url command in the kickstart file without liveimg command, and it failed with a missing YUM package group "core"

url --url=http://<web-server>/<path>

• I'm using PXE boot, not ISO boot. ISO image is not mounted on /run/install/repo when %pre section is executed.
• The following is the kickstart file using liveimg command. This was created upon the ks.cfg file included in the installation ISO.

%pre --log=/tmp/pre.log
mkdir /run/install/repo/Packages
wget http://<web-server>/<path>/redhat-virtualization-host-image-update-4.1-20170417.0.el7_3.noarch.rpm -O /run/install/repo/Packages/redhat-virtualization-host-image-update-4.1-20170417.0.el7_3.noarch.rpm
wget http://<web-server>/<path>/redhat-virtualization-host-productimg-4.1-0.2.el7.x86_64.rpm -O /run/install/repo/Packages/redhat-virtualization-host-productimg-4.1-0.2.el7.x86_64.rpm
cd /tmp
rpm2cpio /run/install/repo/Packages/redhat-virtualization-host-image-update*|cpio -ivd
squashfs=$(find|grep squashfs|grep -v meta)
ln -s $squashfs /tmp/squashfs
%end
liveimg --url=file:///tmp/squashfs
autopart --type=thinp
%post --erroronfail
imgbase layout --init
%end