When I build the documentation on the current CPython code, there is a deprecation warning on the console. 

===== (beginning of output)
% make html
sphinx-build -b html -d build/doctrees -D latex_elements.papersize=  . build/html 
Running Sphinx v1.5.2
...[omitted irrelevant output]...
generating indices... genindex py-modindex
writing additional pages... download index
    WARNING: Now base template defindex.html is deprecated.
 search opensearch
copying images... [100%] faq/python-video-icon.png                                                          
...[omitted irrelevant output]...
build succeeded, 1 warning.

Build finished. The HTML pages are in build/html.
===== (end of output)

This is observed when building documentation from branch master, commit b1dc6b6d5fa20f63f9651df2e7986a066c88ff7d . 
The build command is "cd Doc; make html".

There are other warnings in the output, and I'm dealing with them in a different issue (number to follow). They are easier to fix than this one.

Diagnosis:
Sphinx config file Doc/conf.py:72 invokes the building of template 'indexcontent.html'. 
Doc/tools/templates/indexcontent.html:1 contains Sphinx directive 
`{% extends "defindex.html" %}`.
This invokes file sphinx/sphinx/themes/basic/defindex.html 
[See https://github.com/sphinx-doc/sphinx/blob/8ecd7ff08249739bbc6d900527fe9306592456ab/sphinx/themes/basic/defindex.html ]. Sure enough, it issues a deprecation warning. 

{{ warn('Now base template defindex.html is deprecated.') }}

There's a story behind this file.

Sphinx issue 2986 (https://github.com/sphinx-doc/sphinx/issues/2986) says that this is a very old file, from about the 0.2 version of Sphinx. It wasn't HTML 5 compatible, so they declared it obsolete and threw it out. Well, that lasted only about two weeks.  It became apparent that not only Python's docs, but thousands of other projects, seem to rely on it. So, defindex.html was restored, but with the deprecation warning.

Then, on 1. January 2017, Sphinx deleted defindex.html again. (See https://github.com/sphinx-doc/sphinx/commit/45d3f2e8b279efa9d42068d4109cd97eb3f2d899 ). I can only imagine that, once this change makes it into the public release of Sphinx, Python's documentation, and that of thousands of projects, will break again.

So, it seems like a good idea to proactively remove the dependence on this Sphinx file, before that new Sphinx release comes out. 

Options:

1. Copy the Sphinx defindex.html file into our source tree, and keep using it. Plus points: it's simple and easy. Minus points: the Sphinx licence terms may not permit this.  And, it is not HTML5 compatible, which we might care about.

2. Identify the template which Sphinx intends as a successor to defindex.html, and switch to using that.  I've done a bit of searching, and couldn't find out which template that might be.

3. Reimplement our Doc/tools/templates/indexcontent.html to rely on supported Sphinx template, and replace whatever intermediate content we were using from defindex.html with freshly-written code. 

I don't have a solution in mind for this issue. I just want to get it in the bug list, so we know about it.

The other warnings in the "make html" output are the subject of http://bugs.python.org/issue29521 .

Hello Jim,
    I tried to run `make html` on `/Doc` directory at latest master. I was not able to reproduce this warning message. I am attaching console output I got while building the documentation with this issue. I request you to check that once. Will you re-install the dependancy and check for this issue once again? Many thanks!

I can reproduce it with Sphinx 1.5.2.
Additonally, "None" is shown at top.

ref: https://github.com/sphinx-doc/sphinx/issues/2986

Could docs.python.org use new Sphinx, after fix this issue?

Travis checks doc with Sphinx 1.5.2, but docs.python.org seems using 1.3.3.  It's too old.

Jaysinh, thank you for checking.  From your log, I see you are using Sphinx version 1.3.6.  I am seeing this problem with Sphinx version 1.5.2.  I think you need Sphinx 1.5.2 or later to see the warning message.

I notice my original bug description didn't specify a Sphinx version. Now we know that it needs to be a fairly recent version of Sphinx.

From the discussion in https://github.com/sphinx-doc/sphinx/issues/2986, it looks like the Sphinx team added the warning message at or shortly after the release of 1.5.0.

As for CPython documents, these uses only one assignment statement (``{% set ... %}``) [1]_, one h1 element and one p element [2]_ of defindex.html.
These fragments are used to generate following sentences::

   Python 3.6.0 documentation

   Welcome! This is the documentation for Python 3.6.0, last updated Feb 19, 2017. 

.. [1] https://github.com/sphinx-doc/sphinx/blob/8ecd7ff08249739bbc6d900527fe9306592456ab/sphinx/themes/basic/defindex.html#L11

.. [2] https://github.com/sphinx-doc/sphinx/blob/8ecd7ff08249739bbc6d900527fe9306592456ab/sphinx/themes/basic/defindex.html#L13-L18


Therefore, I suggest that we should make indexcontent.html extend layout.html directly and insert the jinja2 code into indexcontent.html in order to generate the sentences above
(which is much the same option as mixture of JDLH's option 1 and 3).

After I wrote this comment, I notice inada.naoki had created `pull request #165 <https://github.com/python/cpython/pull/165>`_.

New changeset 3eea8c67fa870c6e2b7a521d292afe7fe3e95f58 by GitHub in branch 'master':
bpo-29520: doc: fix deprecation warning from 'defindex' template (GH-165)
https://github.com/python/cpython/commit/3eea8c67fa870c6e2b7a521d292afe7fe3e95f58

New changeset cf44d957ec177be62f5349ef88515190dcfccbd6 by GitHub in branch '2.7':
bpo-29520: doc: fix deprecation warning from 'defindex' template (GH-180)
https://github.com/python/cpython/commit/cf44d957ec177be62f5349ef88515190dcfccbd6

New changeset f0174c69b7b8bd27ee32d96e890d665da29472af by GitHub in branch '3.5':
bpo-29520: doc: fix deprecation warning from 'defindex' template (GH-179)
https://github.com/python/cpython/commit/f0174c69b7b8bd27ee32d96e890d665da29472af

New changeset 7970cd483346dfd7723da214fb27399ecc574095 by GitHub in branch '3.6':
bpo-29520: doc: fix deprecation warning from 'defindex' template (GH-178)
https://github.com/python/cpython/commit/7970cd483346dfd7723da214fb27399ecc574095

New changeset e395c4dbe19115aaab315c2a113b172e9fef307a by GitHub in branch 'master':
bpo-29520: doc: add missing dot (GH-182)
https://github.com/python/cpython/commit/e395c4dbe19115aaab315c2a113b172e9fef307a