Update docutils to 0.19

[pyup-bot]

This PR updates docutils from 0.17.1 to 0.19.

Changelog

0.19

=========================

0.19b1

* Drop support for Python 2.7, 3.5, and 3.6.

* Output changes:

HTML5:
 Wrap groups of footnotes in an ``<aside>`` for easier styling.

 The CSS rule ``.footnote-list { display: contents; }`` can be used to
 restore the behaviour of custom CSS styles.

* After package installation, the CLI commands ``python -m docutils`` and
``docutils`` start the `generic command line front end tool`__.

__ docs/user/tools.htmlgeneric-command-line-front-end

* Support parsing "Markdown" input with 3rd party parsers
myst_, pycmark_, or recommonmark_.

* The default values for the "pep-references", "rfc-base-url",
and "python-home" `configuration settings`_ now use the "https:" scheme.
The PEP-writer template's header is updated to fix links and
resemble the header of official PEPs.

* Various bugfixes and improvements (see HISTORY_).

.. _myst: https://pypi.org/project/myst-docutils
.. _pycmark: https://pypi.org/project/pycmark/
.. _recommonmark: https://pypi.org/project/recommonmark/
.. _configuration settings: docs/user/config.html

0.18.1

===========================

.. Note::

Docutils 0.18.x is the last version supporting Python 2.7, 3.5, and 3.6.

* ``nodes.Node.traverse()`` returns a list again to restore backwards
compatibility (fixes bug 431).
Use ``nodes.Node.findall()`` to get an iterator.

* re-add module ``parsers.rst.directives.html``
(stub, emits deprecation warning and loads
"Meta" directive from ist new place at ``parsers.rst.directives.misc``.)

* Small bugfixes (see HISTORY_).

0.18

=========================

* Output changes:

Identifiers:
 - During `identifier normalization`_, leading number and hyphen
   characters are no longer stripped from a `reference name`_, if the
   id_prefix_ setting is non-empty.

   Example:
     with ``--id-prefix="DU-"``, a section with title "34. May"
     currently gets the identifier key ``DU-may`` and after the
     change the identifier key ``DU-34-may``.

 - The default value for the auto_id_prefix_ setting changed to ``%``:
   "use the tag name as prefix for auto-generated IDs".
   Set auto_id_prefix_ to ``id`` for unchanged auto-IDs.

HTML5:
 - Use the semantic tag <aside> for footnote text and citations, topics
   (except abstract and toc), admonitions, and system messages.
   Use <nav> for the Table of Contents.

 - Make "auto" table column widths the default: Only specify column
   widths, if the `"widths" option`_ is set and not "auto".
   The table-style__ setting "colwidths-grid" restores the current default.

   .. _"widths" option: __ docs/ref/rst/directives.htmltable
   __ docs/user/config.htmltable-style

 - Items of a definition list with class argument "details" are
   converted to `details disclosure elements`_. Example::

     ..class:: details

     Summary
       This additional information should be hidden.

 - Do not add "compound-first", "compound-middle", or "compound-last" to
   elements nested in a compound. Use child selector and ":first-child",
   ":last-child" pseudo classes instead.

 - Use class value "backrefs" instead of "fn-backref" for a span of
   back-references.

 - Write footnote brackets and field term colons to HTML, so that they
   are present also without CSS and when copying text.

 - Move space character between section number and heading into
   "sectnum" span.

`math-output`_: html
 - Support more commands, fix mapping of commands to Unicode characters.
 - Scale variable sized operators and big delimiters with CSS.
 - Don't use <tt> element (deprecated in HTML5).
 - Use STIX fonts if available.

LaTeX:
  `legacy_class_functions`_ setting default changed to "False",
  admonitions are now environments.

* New standard Docutils doctree node: <meta__>.

* New configuration settings:

- [latex writers] legacy_column_widths_ and
- [html5 writer] image_loading_.

* Removed files:
``iepngfix.htc`` and ``blank.gif`` (IE 6 workaround for `s5_html`).

* Removed sub-module:
``parsers.rst.directives.html``
(reversed in release 0.18.1).

* Removed function: utils.unique_combinations()
(obsoleted by itertools.combinations()).

* Removed attributes:

- ``HTMLTranslator.topic_classes``: check ``node.parent.classes`` instead.
- ``nodes.Text.rawsource``: we store the null-escaped text in Text
 nodes since 0.16 so there is no additional information in the
 rawsource.

* Major refactoring and fixes/additions in
``docutils/utils/math/math2html.py`` and
``docutils/utils/math/latex2mathml.py``
(mathematical notation in HTML, cf. `LaTeX syntax for mathematics`_).

* nodes.Node.traverse() returns an iterator instead of a list
(reversed in release 0.18.1).

* Various bugfixes and improvements (see HISTORY_).

Fix spelling errors in documentation and docstrings.
Thanks to Dimitri Papadopoulos.

__ docs/ref/doctree.htmlmeta
.. _identifier normalization:
docs/ref/rst/directives.htmlidentifier-normalization
.. _id_prefix: docs/user/config.htmlid-prefix
.. _auto_id_prefix: docs/user/config.htmlauto-id-prefix
.. _details disclosure elements:
 https://www.w3.org/TR/html52/interactive-elements.html#the-details-element
.. _LaTeX syntax for mathematics: docs/ref/rst/mathematics.html
.. _legacy_column_widths: docs/user/config.htmllegacy-column-widths

Links

• PyPI: https://pypi.org/project/docutils
• Changelog: https://pyup.io/changelogs/docutils/
• Homepage: https://docutils.sourceforge.io/

[pyup-bot]

Closing this in favor of #681