Description of problem:

Since the OSP12 puddle 2017-07-11.7 the openstack-rally package doesn't have dependency on python-sphinx.
It has been remove upstream [1] but the current code seems to still use it.
The rally commands exit with a python trace because the sphinx python module is missing (and not present in the puddle anymore).

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

OSP12 puddle 2017-07-11.7
openstack-rally-0.9.1-0.20170703215956.d32b2d5.el7ost.1.noarch
also tested on the package coming from the latest puddle (2017-07-12.3)
openstack-rally-0.9.1-0.20170707094646.caa9fc0.el7ost.noarch

How reproducible:
100%

Steps to Reproduce:
1. Install openstack-rally package
2. Run rally command

Actual results:
$ rally-manage db create
Traceback (most recent call last):
  File "/usr/bin/rally-manage", line 6, in <module>
    from rally.cli.manage import main
  File "/usr/lib/python2.7/site-packages/rally/cli/manage.py", line 23, in <module>
    from rally.cli import cliutils
  File "/usr/lib/python2.7/site-packages/rally/cli/cliutils.py", line 34, in <module>
    from rally import api
  File "/usr/lib/python2.7/site-packages/rally/api.py", line 30, in <module>
    from rally.common import opts
  File "/usr/lib/python2.7/site-packages/rally/common/opts.py", line 20, in <module>
    from rally import osclients
  File "/usr/lib/python2.7/site-packages/rally/osclients.py", line 25, in <module>
    from rally.common.plugin import plugin
  File "/usr/lib/python2.7/site-packages/rally/common/plugin/plugin.py", line 21, in <module>
    from rally.common.plugin import info
  File "/usr/lib/python2.7/site-packages/rally/common/plugin/info.py", line 18, in <module>
    from sphinx.util import docstrings
ImportError: No module named sphinx.util

Additional info:
[1] https://review.rdoproject.org/r/#/c/7573/