tox -e docs is broken due to py3 compatibility

[Qiming Teng]

In my setup, tox -e docs always starts in py3 environment, it is weird but acceptable.

The problem is that 'tox -e docs' never passes. It is complaining:

TypeError: must use keyword argument for key

This is because we still have some code not py3 compatible.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/252189

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/252189
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=8b1fc0dab55ff195c52003026e0c49bb78fad759
Submitter: Jenkins
Branch: master

commit 8b1fc0dab55ff195c52003026e0c49bb78fad759
Author: tengqm <email address hidden>
Date: Tue Dec 1 22:14:04 2015 -0500

    Fix tox -e docs build in py3

    The current script doesn't work under py3. It is using some features
    that are deprecated in py3. This patch fixes it.

    Change-Id: I475ebd721c5a49a96f86450d4972ea21a42a50b7
    Closes-Bug: #1521837

[Thierry Carrez (ttx)]

This issue was fixed in the openstack/heat 6.0.0.0b1 development milestone.