Comment 4 for bug 1578404

After the merge of this change I got the following error when running with the parameter --template-only:

kolla-build --config-file kolla-build.conf --template-only neutron
INFO:kolla.cmd.build:Found the docker image folder at /usr/local/share/kolla/docker
INFO:kolla.cmd.build:Dockerfiles are generated in /tmp/kolla-2016-05-31_16-31-59_ctuce_/docker
Traceback (most recent call last):
  File "/usr/local/bin/kolla-build", line 10, in <module>
    sys.exit(main())
  File "/usr/local/lib/python2.7/dist-packages/kolla/cmd/build.py", line 795, in main
    bad_results, good_results, unmatched_results = run_build()
TypeError: 'NoneType' object is not iterable