yum -y doesn't report an error when packages are missing (see [1] for
upstream discussion). Thus we run the output of yum through a small
awk script looking for missing packages output.
The one change required for RHEL is that python-wsgiref is included in
the distro python, so doesn't need a separate package.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=965567
Change-Id: I9908ff4edbf2b0d961d25837a08a34e1417bbb02
b27f16d716