while I perform a standard installation that includes also the pattern:
  KVM Virtualization Host and tools
the installation process pauses with the following error message:

Subprocess failed. Error: RPM failed: /var/tmp/rpm-tmp.9xnoqh: line 32:
groupadd: command not found
/var/tmp/rpm-tmp.9xnoqh: line 34: useradd: command not found
error: %prein(unbound-anchor-1.6.8-lp151.5.1.x86_64) scriptlet failed, exit
status 127
error: unbound-anchor-1.6.8-lp151.5.1.x86_64: install failed

The problem is that unbound-anchor is installed before shadow and at that time
the binaries groupadd and useradd used in the preinstall scriptlet, are not
available yet.

A possible fix is to add this line in unbound.spec:

 %if %{with python}
 BuildRequires:  swig
 %endif
 PreReq:         pwdutils
+PreReq:         shadow
 Requires:       ldns >= %{ldns_version}
 # until we figured something else out for the unbound-anchor part in the
systemd unit file
 Requires:       sudo

This is it about the unbound-anchor bug. But while I'm at it, i would like to
remember that selecting the KVM Virtualization Host pattern triggers also bug
903889 which is more than 4 years old and apparently nobody wants to fix it.