Initial commit of python-pluggy
Summary: Initial commit of python-pluggy. Needed as a rundep by the testing framework "tox".
Test Plan: Tested that the module was available using "python2 -m pluggy" and "python3 -m pluggy" as well as by running "tox --help" where it didn't error out saying pluggy wasn't available.
Reviewers: Triage Team, ikey
Reviewed By: Triage Team, ikey
Subscribers: ikey, JoshStrobl
Differential Revision: https://dev.solus-project.com/D137