pbr alters sdist output for non-pbr-using projects

[Robert Collins]

pip$ python setup.py sdist
running sdist
running egg_info
writing pbr to pip.egg-info/pbr.json

This only happens in git trees AFAICT.

Marking critical since this is a fairly huge nono.

[Robert Collins (lifeless)]

the bug is that pbr should only be active, and only change things, for setup's where setup(pbr=True).

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/217528

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/217528
Committed: https://git.openstack.org/cgit/openstack-dev/pbr/commit/?id=8047f2feafeead5f4913f9ab1d7d2c6d0ccf79e0
Submitter: Jenkins
Branch: master

commit 8047f2feafeead5f4913f9ab1d7d2c6d0ccf79e0
Author: Sachi King <email address hidden>
Date: Thu Aug 27 15:52:03 2015 +1000

    Have pbr egg_info.writer check PBR is enabled

    PBR is currently creating a pbr.json for any install originating from a
    git tree as pbr_json is an entry point for egg_info.writers. If pbr is
    not set to True in setup() we now exit before doing any work.

    Change-Id: Ia37e37c22c2396f6a10aa2075ea8c501e571fee3
    Closes-Bug: 1483067