Description of problem:
Taken from mailing list while trying to debug my problem with python-oauthlib not working through Koji/EPEL7 builds, but working perfectly fine using COPR/EPEL7. 

...python-oauthlib is in both epel7 and rhel7 base repo.

Koji operates on source packages, so when both epel7 and rhel7 have the
same package name, epel7 wins. The epel7 python-oauthlib package does
not provide a python2-oauthlib subpackage (it only has python-oauthlib).
Because it's using the epel7 one, it ignores everything the rhel7 one
creates, so you don't get the python2-oauthlib from there either.

In Copr the newest package wins, so you get the rhel7 one because it's
much newer than the old epel7 one.

- Credit to Kevin Fenzi for summarizing the above.

The request is to just retire the python-oauthlib

Version-Release number of selected component (if applicable):

Entire Koji/EPEL7 environment

How reproducible:

Every single time.  Here is a failing package build using Koji:
https://koji.fedoraproject.org/koji/taskinfo?taskID=33139296

Here the exact same src.rpm building perfectly fine on COPR
https://copr.fedorainfracloud.org/coprs/build/861900/

Steps to Reproduce:
1. wget https://copr-be.cloud.fedoraproject.org/results/lead2gold/apprise/epel-7-x86_64/00861900-python-apprise/python-apprise-0.7.3-1.el7.nuxref.src.rpm
2. <assuming you can build with koji>
3. koji build --scratch epel7 python-apprise-0.7.3-1.el7.nuxref.src.rpm

Actual results:

...
DEBUG util.py:490:  BUILDSTDERR: No matching package to install: 'python2-oauthlib'
DEBUG util.py:490:  BUILDSTDERR: Not all dependencies satisfied
DEBUG util.py:490:  BUILDSTDERR: Error: Some packages could not be found.
...

Expected results:
RPM to build just fine

Additional info:
Mailing list post which lead me to creating this ticket:
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/ANW32KNP22TKPV3PX2U72V2LEZYGGYN6/