Remove matplotlib requirement for building docs

See gh-10003

We weren't actually using most of these extensions, and the one we were
using can be replaced by a standard Sphinx directive.

docs/source/api/index.rst

@@ -1,12 +1,12 b''
 .. _api-index:
 
 ###################
   The IPython API
 ###################
 
-.. htmlonly::
+.. only:: html
 
    :Release: |version|
    :Date: |today|
 
 .. include:: generated/gen.txt

docs/source/conf.py

@@ -1,298 +1,295 b''
 # -*- coding: utf-8 -*-
 #
 # IPython documentation build configuration file.
 
 # NOTE: This file has been edited manually from the auto-generated one from
 # sphinx.  Do NOT delete and re-generate.  If any changes from sphinx are
 # needed, generate a scratch one and merge by hand any new fields needed.
 
 #
 # This file is execfile()d with the current directory set to its containing dir.
 #
 # The contents of this file are pickled, so don't put values in the namespace
 # that aren't pickleable (module imports are okay, they're removed automatically).
 #
 # All configuration values have a default value; values that are commented out
 # serve to show the default value.
 
 import sys, os
 
 ON_RTD = os.environ.get('READTHEDOCS', None) == 'True'
 
 if ON_RTD:
     # Mock the presence of matplotlib, which we don't have on RTD
     # see
     # http://read-the-docs.readthedocs.io/en/latest/faq.html
     tags.add('rtd')
 
     # RTD doesn't use the Makefile, so re-run autogen_{things}.py here.
     for name in ('config', 'api', 'magics', 'shortcuts'):
         fname = 'autogen_{}.py'.format(name)
         fpath = os.path.abspath(os.path.join('..', fname))
         with open(fpath) as f:
             exec(compile(f.read(), fname, 'exec'), {
                 '__file__': fpath,
                 '__name__': '__main__',
             })
 else:
     import sphinx_rtd_theme
     html_theme = "sphinx_rtd_theme"
     html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 # If your extensions are in another directory, add it here. If the directory
 # is relative to the documentation root, use os.path.abspath to make it
 # absolute, like shown here.
 sys.path.insert(0, os.path.abspath('../sphinxext'))
 
 # We load the ipython release info into a dict by explicit execution
 iprelease = {}
 exec(compile(open('../../IPython/core/release.py').read(), '../../IPython/core/release.py', 'exec'),iprelease)
 
 # General configuration
 # ---------------------
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
 extensions = [
-    'matplotlib.sphinxext.mathmpl',
-    'matplotlib.sphinxext.only_directives',
-    'matplotlib.sphinxext.plot_directive',
     'sphinx.ext.autodoc',
     'sphinx.ext.autosummary',
     'sphinx.ext.doctest',
     'sphinx.ext.inheritance_diagram',
     'sphinx.ext.intersphinx',
     'IPython.sphinxext.ipython_console_highlighting',
     'IPython.sphinxext.ipython_directive',
     'sphinx.ext.napoleon',  # to preprocess docstrings
     'github',  # for easy GitHub links
     'magics',
 ]
 
 if ON_RTD:
     # Remove extensions not currently supported on RTD
     extensions.remove('matplotlib.sphinxext.only_directives')
     extensions.remove('matplotlib.sphinxext.mathmpl')
     extensions.remove('matplotlib.sphinxext.plot_directive')
     extensions.remove('IPython.sphinxext.ipython_directive')
     extensions.remove('IPython.sphinxext.ipython_console_highlighting')
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 
 # The suffix of source filenames.
 source_suffix = '.rst'
 
 rst_prolog = ''
 
 def is_stable(extra):
     for ext in {'dev', 'b', 'rc'}:
         if ext in extra:
             return False
     return True
 
 if is_stable(iprelease['_version_extra']):
     tags.add('ipystable')
 else:
     tags.add('ipydev')
     rst_prolog += """
 .. warning::
 
     This documentation covers a development version of IPython. The development
     version may differ significantly from the latest stable release.
 """
 
 rst_prolog += """
 .. important::
 
     This documentation covers IPython versions 6.0 and higher. Beginning with
     version 6.0, IPython stopped supporting compatibility with Python versions
     lower than 3.3 including all versions of Python 2.7.
 
     If you are looking for an IPython version compatible with Python 2.7,
     please use the IPython 5.x LTS release and refer to its documentation (LTS
     is the long term support release).
 
 """
 
 # The master toctree document.
 master_doc = 'index'
 
 # General substitutions.
 project = 'IPython'
 copyright = 'The IPython Development Team'
 
 # ghissue config
 github_project_url = "https://github.com/ipython/ipython"
 
 # numpydoc config
 numpydoc_show_class_members = False # Otherwise Sphinx emits thousands of warnings
 numpydoc_class_members_toctree = False
 
 # The default replacements for |version| and |release|, also used in various
 # other places throughout the built documents.
 #
 # The full version, including alpha/beta/rc tags.
 release = "%s" % iprelease['version']
 # Just the X.Y.Z part, no '-dev'
 version = iprelease['version'].split('-', 1)[0]
 
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
 #today = ''
 # Else, today_fmt is used as the format for a strftime call.
 today_fmt = '%B %d, %Y'
 
 # List of documents that shouldn't be included in the build.
 #unused_docs = []
 
 # Exclude these glob-style patterns when looking for source files. They are
 # relative to the source/ directory.
 exclude_patterns = ['whatsnew/pr']
 
 
 # If true, '()' will be appended to :func: etc. cross-reference text.
 #add_function_parentheses = True
 
 # If true, the current module name will be prepended to all description
 # unit titles (such as .. function::).
 #add_module_names = True
 
 # If true, sectionauthor and moduleauthor directives will be shown in the
 # output. They are ignored by default.
 #show_authors = False
 
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'
 
 # Set the default role so we can use `foo` instead of ``foo``
 default_role = 'literal'
 
 # Options for HTML output
 # -----------------------
 
 # The style sheet to use for HTML and HTML Help pages. A file of that name
 # must exist either in Sphinx' static/ path, or in one of the custom paths
 # given in html_static_path.
 # html_style = 'default.css'
 
 
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
 #html_title = None
 
 # The name of an image file (within the static path) to place at the top of
 # the sidebar.
 #html_logo = None
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['_static']
 
 # Favicon needs the directory name
 html_favicon = '_static/favicon.ico'
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
 html_last_updated_fmt = '%b %d, %Y'
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
 #html_use_smartypants = True
 
 # Custom sidebar templates, maps document names to template names.
 #html_sidebars = {}
 
 # Additional templates that should be rendered to pages, maps page names to
 # template names.
 html_additional_pages = {
     'interactive/htmlnotebook': 'notebook_redirect.html',
     'interactive/notebook': 'notebook_redirect.html',
     'interactive/nbconvert': 'notebook_redirect.html',
     'interactive/public_server': 'notebook_redirect.html',
 }
 
 # If false, no module index is generated.
 #html_use_modindex = True
 
 # If true, the reST sources are included in the HTML build as _sources/<name>.
 #html_copy_source = True
 
 # If true, an OpenSearch description file will be output, and all pages will
 # contain a <link> tag referring to it.  The value of this option must be the
 # base URL from which the finished HTML is served.
 #html_use_opensearch = ''
 
 # If nonempty, this is the file name suffix for HTML files (e.g. ".xhtml").
 #html_file_suffix = ''
 
 # Output file base name for HTML help builder.
 htmlhelp_basename = 'ipythondoc'
 
 intersphinx_mapping = {'python': ('https://docs.python.org/3/', None),
                        'rpy2': ('https://rpy2.readthedocs.io/en/version_2.8.x/', None),
                        'traitlets': ('https://traitlets.readthedocs.io/en/latest/', None),
                        'jupyterclient': ('https://jupyter-client.readthedocs.io/en/latest/', None),
                        'ipyparallel': ('https://ipyparallel.readthedocs.io/en/latest/', None),
                        'jupyter': ('https://jupyter.readthedocs.io/en/latest/', None),
                       }
 
 # Options for LaTeX output
 # ------------------------
 
 # The paper size ('letter' or 'a4').
 latex_paper_size = 'letter'
 
 # The font size ('10pt', '11pt' or '12pt').
 latex_font_size = '11pt'
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, document class [howto/manual]).
 
 latex_documents = [
     ('index', 'ipython.tex', 'IPython Documentation',
      u"""The IPython Development Team""", 'manual', True),
     ('parallel/winhpc_index', 'winhpc_whitepaper.tex',
      'Using IPython on Windows HPC Server 2008',
      u"Brian E. Granger", 'manual', True)
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
 # the title page.
 #latex_logo = None
 
 # For "manual" documents, if this is true, then toplevel headings are parts,
 # not chapters.
 #latex_use_parts = False
 
 # Additional stuff for the LaTeX preamble.
 #latex_preamble = ''
 
 # Documents to append as an appendix to all manuals.
 #latex_appendices = []
 
 # If false, no module index is generated.
 latex_use_modindex = True
 
 
 # Options for texinfo output
 # --------------------------
 
 texinfo_documents = [
   (master_doc, 'ipython', 'IPython Documentation',
    'The IPython Development Team',
    'IPython',
    'IPython Documentation',
    'Programming',
    1),
 ]
 
 modindex_common_prefix = ['IPython.']
 
 
 # Cleanup
 # -------
 # delete release info to avoid pickling errors from sphinx
 
 del iprelease

docs/source/index.rst

@@ -1,111 +1,111 b''
 .. _introduction:
 
 =====================
 IPython Documentation
 =====================
 
-.. htmlonly::
+.. only:: html
 
    :Release: |release|
    :Date: |today|
 
 Welcome to the official IPython documentation
 
 IPython provides a rich toolkit to help you make the most out of using Python
 interactively.  Its main components are:
 
 * A powerful interactive Python shell
 
 * A `Jupyter <http://jupyter.org/>`_ kernel to work with Python code in Jupyter
   notebooks and other interactive frontends.
 
 The enhanced interactive Python shells and kernel have the following main
 features:
 
 * Comprehensive object introspection.
 
 * Input history, persistent across sessions.
 
 * Caching of output results during a session with automatically generated
   references.
 
 * Extensible tab completion, with support by default for completion of python
   variables and keywords, filenames and function keywords.
 
 * Extensible system of 'magic' commands for controlling the environment and
   performing many tasks related either to IPython or the operating system.
 
 * A rich configuration system with easy switching between different setups
   (simpler than changing $PYTHONSTARTUP environment variables every time).
 
 * Session logging and reloading.
 
 * Extensible syntax processing for special purpose situations.
 
 * Access to the system shell with user-extensible alias system.
 
 * Easily embeddable in other Python programs and GUIs.
 
 * Integrated access to the pdb debugger and the Python profiler.
 
 
 The Command line interface inherits all the above functionality and posses 
  
 * real multi-line editing.
  
 * syntax highlighting as you type
 
 * integration with command line editor for a better workflow.
 
 The kernel also have its share of feature, when used with a compatible frontend
 it allows for:
 
 * rich display system for object allowing to display Html, Images, Latex,Sounds
   Video.
 
 * interactive widgets with the use of the ``ipywidgets`` package.
 
 
 This documentation will walk through most of the features of the IPython
 command line and kernel, as well as describe the internals mechanisms in order
 to improve your Python workflow.
 
 You can always find the table of content for this documentation in the left
 sidebar, allowing you to come back on previous section if needed, or skip ahead. 
 
 
 The latest development version is always available from IPython's `GitHub
 repository <http://github.com/ipython/ipython>`_.
 
 
 
 
 .. toctree::
    :maxdepth: 1
    :hidden:
 
    self
    overview
    whatsnew/index
    install/index
    interactive/index
    config/index
    development/index
    coredev/index
    api/index
    about/index
 
 .. seealso::
 
    `Jupyter documentation <http://jupyter.readthedocs.io/en/latest/>`__
      The Notebook code and many other pieces formerly in IPython are now parts
      of Project Jupyter.
    `ipyparallel documentation <http://ipyparallel.readthedocs.io/en/latest/>`__
      Formerly ``IPython.parallel``.
 
 
-.. htmlonly::
+.. only:: html
    * :ref:`genindex`
    * :ref:`modindex`
    * :ref:`search`