transaction: use 'util.copyfile' for creating backup
Using 'copyfile' (single file) instead of 'copyfiles' (tree) will ensures
destination file will be overwritten. This will prevent some abort if backup
file are left in place for random reason.
It also seems more correct.
FROM centos:centos7
RUN yum install -y gcc
RUN yum install -y python-devel python-docutils
RUN yum install -y make
RUN yum install -y rpm-build
RUN yum install -y gettext
RUN yum install -y tar
# For creating repo meta data
RUN yum install -y createrepo