livecd-creator missing rubygem-fast_gettext

Hello there,

I'm following knowledge article to build an Discovery image:
https://access.redhat.com/documentation/en-us/red_hat_satellite/6.7/html/provisioning_guide/configuring-the-discovery-service#building-a-discovery-image

where I've run to an strange issue using livecd-creator :

livecd-creator --title="Discovery-Image" \

--compression-type=xz \
--cache=var/cache/build-fdi \
--config /usr/share/foreman-discovery-image/foreman-discovery-image.ks \
--fslabel fdi \
--tmpdir /var/tmp
['/sbin/mkfs.ext4', '-F', '-L', '_fdi', '-m', '1', '-b', '4096', '/dev/loop0']
Skipping (/sys/fs/selinux,/sys/fs/selinux) because source doesn't exist.
Error creating Live CD : Failed to find package 'rubygem-fast_gettext' : No package(s) available to install

required packages are installed :
rpm -qa | egrep "rubygem-fast_gettext|rubygem-rake|rubygems"
tfm-rubygem-fast_gettext-1.4.1-3.el7sat.noarch
rh-ruby25-rubygems-2.7.6.2-7.el7.noarch
rubygem-rake-0.9.6-36.el7.noarch
rubygems-2.0.14.1-36.el7.noarch
rubygem-fast_gettext-1.1.0-4.el7sat.noarch
rh-ruby25-rubygem-rake-12.3.0-7.el7.noarch

so they should be available but somehow livecd-creator is not able to find installed rubygem-fast_gettext.

did anyone run into similar issue ?

cat /etc/*release
NAME="Red Hat Enterprise Linux Server"
VERSION="7.9 (Maipo)"

satellite version : 6.7.4

Thanks for any advice,

Juraj