contrib/docker/centos7

manifest: fix possible SEGV caused by uninitialized lazymanifest fields

Before, uninitialized self->pydata would be passed to lazymanifest_dealloc()
on OOM, and Py_DECREF(self->pydata) would crash if we were unlucky.

It's still wrong to do malloc() thingy in tp_init because __init__() may be
called more than once [1], but I don't want to go a step further in stable
branch.

 [1]: https://docs.python.org/2/c-api/typeobj.html#c.PyTypeObject.tp_new
 "The tp_new function should ... do only as much further initialization as
  is absolutely necessary. Initialization that can safely be ignored or
  repeated should be placed in the tp_init handler."

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