Install the OpenStack command-line clients in End User Guide

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [x ] This doc is inaccurate in this way: Prerequisites should be updated for Python. Python3 is now supported for the openstack client.
- [ ] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

If you have a troubleshooting or support issue, use the following resources:

 - Ask OpenStack: http://ask.openstack.org
 - The mailing list: http://lists.openstack.org
 - IRC: 'openstack' channel on Freenode

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Release: 1.0.0 on 2019-08-23 19:37
SHA: f80f22b2537844fc48e4f78bfb9eb664ad1f1280
Source: http://git.openstack.org/cgit/openstack/openstack-manuals/tree/doc/user-guide/source/common/cli-install-openstack-command-line-clients.rst
URL: https://docs.openstack.org/newton/user-guide/common/cli-install-openstack-command-line-clients.html