Update docutils to 0.18.1

[pyup-bot]

This PR updates docutils from 0.15.2 to 0.18.1.

Changelog

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).

* 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``
(Meta directive moved to ``parsers.rst.directives.misc``.)

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

* Removed attribute: ``HTMLTranslator.topic_classes``
(check node.parent.classes instead).

* 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.

* 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

0.17.1

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

* Bug fixes (for details see the Docutils `HISTORY`_).

0.17

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

* Numerous bug fixes and improvements
(for details see the Docutils `HISTORY`_).

* Installing with ``setup.py`` now requires setuptools_.
Alternatively, install with pip_.

* The generic command line front end tool docutils-cli.py_ allows
the free selection of reader, parser, and writer components.

* Support Arabic language.

* New, **experimental** wrapper to integrate the `recommonmark`__
Markdown parser for use with Docutils.
Currently only tested with recommonmark version 0.4.0.

__ https://pypi.org/project/recommonmark/

* HTML5 writer:

- New option embed_images_.

- Use semantic tags (for details see the Docutils `HISTORY`_).

- Change the `initial_header_level`_ setting's default to "2", as browsers
 use the `same style for <h1> and <h2> when nested in a section`__.

- New optional style ``responsive.css``, adapts to different screen
 sizes.

- Move non-essential styling from ``minimal.css`` to ``plain.css``
 rsp. ``responsive.css``.

- Show code line numbers as pseudo-elements so they are skipped when
 copying the code block from the page.

.. _initial_header_level: docs/user/config.htmlinitial-header-level
__ https://stackoverflow.com/questions/39547412/same-font-size-for-h1-and-h2-in-article
.. _embed_images: docs/user/config.htmlembed-images

* LaTeX writer:

- New configuration setting `legacy_class_functions`_.

- The special value "auto" for the `graphicx_option`_ setting
 is no longer supported (it never worked for xetex/luatex).

- `Styling commands`__ using the legacy ``\docutilsrole`` prefix are
 now ignored. Use ``\DUrole``.

 __ docs/user/latex.htmlclasses

- Most helper commands and element definitions are now defined in the
 LaTeX package `docutils.sty`_ and only inserted in the document
 preamble if the stylesheet__ setting does not lists "docutils".

 __ docs/user/config.htmlstylesheet-latex-writers

- Remove legacy LaTeX stylesheet ``docutils-05-compat.sty``.

.. _setuptools: https://pypi.org/project/setuptools/
.. _pip: https://pypi.org/project/pip/
.. _docutils-cli.py: docs/user/tools.htmldocutils-cli-py
.. _legacy_class_functions: docs/user/config.htmllegacy-class-functions
.. _graphicx_option: docs/user/config.htmlgraphicx-option
.. _docutils.sty: https://ctan.org/pkg/docutils

0.16

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

.. Note::

Docutils 0.15.x is the last version supporting Python 2.6, 3.3 and 3.4.

Docutils 0.16.x supports Python 2.7 and Python >= 3.5 natively,
without the use of the ``2to3`` tool.

* reStructuredText:

- Keep `backslash escapes`__ in the document tree. This allows, e.g.,
 escaping of author-separators in `bibliographic fields`__.

__ http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html#escaping-mechanism
__ docs/ref/rst/restructuredtext.htmlbibliographic-fields

* LaTeX writer:

- Informal titles of type "rubric" default to bold-italic and left aligned.
- Deprecate ``\docutilsrole`` prefix for styling commands:
 use ``\DUrole`` instead.
- Fix topic subtitle.
- Add "latex writers" to the `config_section_dependencies`.
- Ignore classes for `rubric` elements
 (class wrapper interferes with LaTeX formatting).

* tools/buildhtml.py

- New option "--html-writer" allows to select "html__" (default),
 "html4" or "html5".

__ html: docs/user/html.htmlhtml

* docutils/io.py

- Remove the `handle_io_errors` option from io.FileInput/Output.

* docutils/nodes.py

- If `auto_id_prefix`_ ends with "%", this is replaced with the tag name.

.. _auto_id_prefix: docs/user/config.htmlauto-id-prefix

* Various bugfixes and improvements (see HISTORY_).

Links

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