added epel priority

Dockerfile

@@ -7,8 +7,9 @@ LABEL version="1.0"
 ENV NSTREAM_ENABLED=0
 
 # OSG Middleware
+RUN yum -y install yum-priorities
 RUN rpm -Uvh https://repo.opensciencegrid.org/osg/3.4/osg-3.4-el7-release-latest.rpm
-RUN yum clean all
+RUN sed "7i priority=99" -i /etc/yum.repos.d/epel.repo
 
 # Core deps
 RUN yum -y install voms globus-gsi-sysconfig globus-gsi-cert-utils globus-gssapi-gsi globus-gss-assist \