F17 yum/rpm not running groupadd in %pre scripts

[Chuck Anderson]

I ran into a comedy of errors today after I did a new F17 installation
yesterday.  Here are a couple:

https://bugzilla.redhat.com/show_bug.cgi?id=848148
Error in PREIN scriptlet in rpm package wireshark-1.6.9-1.fc17.x86_64

(and why does yum still let the transaction succeed, creating problems
in the RPMDB, broken dependencies?)

https://bugzilla.redhat.com/show_bug.cgi?id=845671
"Directory '/var/run/screen' must have mode 777." when opening screen

(and why does systemd-tmpfiles completely fail to start when there is
a missing group--it should fail gracefully, allowing the other
tmpfiles stuff to run and the service as a whole to run)

Both of these are traceable to missing entries in /etc/group.  In the
former cae, there is an explicit "Error in PREIN" script during
instalation.  In the latter case, there is only a warning and
installation proceeds:

Running Transaction
  Installing : screen-4.1.0-0.9.20120314git3c2946.fc17.x86_64               1/1 
warning: group screen does not exist - using root
warning: group screen does not exist - using root

So what is going on with %pre not running groupadd properly?  Are there
any known issues in this area?

Thanks.