Update sphinx to 1.8.1

[pyup-bot]

This PR updates Sphinx from 1.8.0 to 1.8.1.

Changelog

1.8.1

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

Incompatible changes
--------------------

* LaTeX ``\pagestyle`` commands have been moved to the LaTeX template. No
changes in PDF, except possibly if ``\sphinxtableofcontents``, which
contained them, had been customized in :file:`conf.py`. (refs: 5455)

Bugs fixed
----------

* 5418: Incorrect default path for sphinx-build -d/doctrees files
* 5421: autodoc emits deprecation warning for :confval:`autodoc_default_flags`
* 5422: lambda object causes PicklingError on storing environment
* 5417: Sphinx fails to build with syntax error in Python 2.7.5
* 4911: add latexpdf to make.bat for non make-mode
* 5436: Autodoc does not work with enum subclasses with properties/methods
* 5437: autodoc: crashed on modules importing eggs
* 5433: latex: ImportError: cannot import name 'DEFAULT_SETTINGS'
* 5431: autodoc: ``autofunction`` emits a warning for callable objects
* 5457: Fix TypeError in error message when override is prohibited
* 5453: PDF builds of 'howto' documents have no page numbers
* 5463: mathbase: math_role and MathDirective was disappeared in 1.8.0
* 5454: latex: Index has disappeared from PDF for Japanese documents
* 5432: py domain: ``:type:`` field can't process ``:term:`` references
* 5426: py domain: TypeError has been raised for class attribute

Links

• PyPI: https://pypi.org/project/sphinx
• Changelog: https://pyup.io/changelogs/sphinx/
• Homepage: http://sphinx-doc.org/

[coveralls]

Coverage remained the same at 100.0% when pulling 865bc3c on pyup-update-sphinx-1.8.0-to-1.8.1 into 255cf20 on master.