contrib/docker/centos7

tests: fix get-with-headers.py on python3 when writing to stdout

Differential Revision: https://phab.mercurial-scm.org/D2306

FROM centos:centos7
RUN yum install -y \
	gcc \
	gettext \
	make \
	python-devel \
	python-docutils \
	rpm-build \
	tar

# For creating repo meta data
RUN yum install -y createrepo