A lot of dependencies for pungi are not in RHEL and as such should not be present in the buildroot. This is a problem for the createiso script that runs in a runroot. This patch should reduce dependencies of the script to reduce the footprint on the buildroot, which might be enough according to @jblazek.

There should be no change in functionality,

To fully take advantage of this, some changes will need to happen to the packaging. I wrote a patch for the spec:
https://paste.fedoraproject.org/396141/60623014/

It creates two additional subpackages: python2-pungi and pungi-createiso. The former contains all Python modules, the latter only installs the one executable script. The composer boxes are still expected to install original pungi package. Both pungi and pungi-createiso have a new dependency on python2-pungi.

A scratch build with these changes is here: http://koji.fedoraproject.org/koji/taskinfo?taskID=15032373

I had to also add a build-requires on textlive-capt-of and textlive-eqparbox to fix building documentation in PDF.