reno 2.0.0 broke puppet release note jobs

[Alex Schultz]

2016-12-21 20:46:11.167685 | Exception occurred:
2016-12-21 20:46:11.169290 | File "/home/jenkins/workspace/gate-puppet-neutron-releasenotes/.tox/releasenotes/local/lib/python2.7/site-packages/reno/scanner.py", line 388, in _get_branch_base
2016-12-21 20:46:11.169321 | return tags[-1]

http://logs.openstack.org/17/413717/1/gate/gate-puppet-nova-releasenotes/cbddac5/console.html#_2016-12-21_21_22_17_016740
http://logs.openstack.org/57/413757/2/check/gate-puppet-neutron-releasenotes/39ba5ca/console.html#_2016-12-21_20_46_11_195736

It appears that it does not like parsing the git history for these modules
http://eavesdrop.openstack.org/irclogs/%23openstack-release/%23openstack-release.2016-12-21.log.html#t2016-12-21T22:59:55

[Doug Hellmann (doug-hellmann)]

https://review.openstack.org/414161

[Doug Hellmann (doug-hellmann)]

This will be included in 2.0.1 shortly.