It turns out this problem is caused by the installation of this side
repository:
 city-fan.org-release-1-12.rhel6.noarch 
Specifically of this package:
 libxml2-2.9.2-4.0.cf.rhel6.x86_64 
which changes libxml2 so it depends on a new library (liblzma).
New supermin (version 5) in RHEL 7.1 can deal with these kinds of
changes automatically, but the version of supermin in RHEL 6 (version 3)
cannot, at least not without rebuilding libguestfs.
Rich.
-- 
Richard Jones, Virtualization Group, Red Hat 
http://people.redhat.com/~rjones
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