Use stomppy 3.1.6 in the container image

Using the latest version would require rewriting some of the messaging
pieces.

Signed-off-by: Hunor Csomortáni <csomh@redhat.com>

openshift/backend/Dockerfile

@@ -12,21 +12,13 @@ ARG mbs_rpm=module-build-service
 ARG mbs_messaging_umb_rpm
 
 RUN dnf -y install \
+            python2-pungi \
+            python2-psycopg2 \
+            https://dl.fedoraproject.org/pub/epel/7Server/x86_64/Packages/s/stomppy-3.1.6-3.el7.noarch.rpm \
             $mbs_rpm \
             $mbs_messaging_umb_rpm \
-            python2-psycopg2 \
     && dnf -y clean all
 
-# 1. Use latest stomp.py - hackish way for making this change, until there is
-#    sufficient proof that newer versions don't break mbs_messaging_umb
-#
-# 2. Install python2-docopt - required by the latest version of stomp.py
-#
-# 3. Install python2-pungi - to make MBS RPMs built for RHEL work with a Fedora
-#    base image
-RUN sed -i 's/==3\.1\.6//g' /usr/lib/python2.7/site-packages/mbs_messaging_umb-*-py2.7.egg-info/requires.txt \
-    && dnf -y install python2-docopt python2-pungi \
-    && dnf -y clean all
 
 VOLUME ["/etc/module-build-service", "/etc/fedmsg.d", "/etc/mbs-certs"]
 ENTRYPOINT fedmsg-hub