Fix docs builds for current Ubuntu versions

Need to use python3. Update the readme accordingly.
Update tox.ini for current tox.

Change-Id: Ie225d08850507dab743b6e58474839a5d48a2f06

README.rst

@@ -7,7 +7,7 @@ API-Site repository
 +++++++++++++++++++
 
 This repository contains the index page for
-https://developer.openstack.org in the `www` directory.
+https://developer.openstack.org in the ``www`` directory.
 
 To complete code reviews in this repository, use the standard
 OpenStack Gerrit `workflow <https://review.opendev.org>`_.
@@ -23,9 +23,9 @@ Prerequisites
 To build the documentation locally, you must install Python and
 `Python Tox <https://tox.readthedocs.io/en/latest/>`_.
 
-To install Tox for Ubuntu 14.04 or later::
+To install Tox and dependencies for Ubuntu 22.04 or later::
 
-    apt-get install python-tox python-dev libxml2-dev libxslt1-dev
+    apt-get install python3-tox python3-dev libxml2-dev libxslt1-dev
 
 To build all the documentation after installing Python and Tox::
 

bindep.txt

@@ -1,7 +1,7 @@
 # This is a cross-platform list tracking distribution packages needed by tests;
 # see https://docs.openstack.org/infra/bindep/ for additional information.
 
-python-dev [platform:dpkg]
+python3-dev [platform:dpkg]
 python-devel [platform:rpm]
 zlib-devel [platform:rpm]
 zlib1g-dev [platform:dpkg]

tox.ini

@@ -8,11 +8,12 @@ basepython = python3
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt
-whitelist_externals =
+allowlist_externals =
    bash
    mkdir
    mv
    rsync
+   {toxinidir}/tools/build-index.sh
 
 [testenv:venv]
 commands = {posargs}