Config file for SL7.5 in mock

[John Pilkington]

I have successfully used mock in Fedora 27 and Fedora 28 to build rpms 
to run under Scientific Linux (as well as ones to run natively.)

At first I used a locally written config file, but more recently 
/etc/mock/epel-7-x86_64-rpmfusion-free.cfg has worked.

It is based on /etc/mock/epel-7.cfg, which is also installed in SL, but 
refers to, and uses, the centos repos.  Are conflicts likely?  Is there 
an SL version?

John P