Use altairplot Sphinx directive of sphinxext_altair package (#3056)

* Use altairplot Sphinx directive of sphinxext_altair package

* Use sphinxext_altair package from pypi

* Add note about sphinxext-altair package in release 5

doc/conf.py

@@ -12,8 +12,8 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import sys
 import os
+import sys
 from datetime import datetime
 
 # If extensions (or modules to document with autodoc) are in another directory,
@@ -36,7 +36,7 @@
     "sphinx.ext.coverage",
     "sphinx.ext.githubpages",
     "numpydoc.numpydoc",
-    "sphinxext.altairplot",
+    "sphinxext_altair.altairplot",
     "sphinxext.altairgallery",
     "sphinxext.schematable",
     "sphinx_copybutton",

doc/releases/changes.rst

@@ -64,6 +64,7 @@ Backward-Incompatible Changes
 - Removed the Vega-Lite 3 and 4 wrappers (#2847).
 - Removed the deprecated datasets.py (#3010).
 - In regards to the grammar changes listed above, the old terminology will still work in many basic cases.  On the other hand, if that old terminology gets used at a lower level, then it most likely will not work.  For example, in the current version of :ref:`gallery_scatter_with_minimap`, two instances of the key ``param`` are used in dictionaries to specify axis domains.  Those used to be ``selection``, but that usage is not compatible with the current Vega-Lite schema.
+- Removed the ``altair.sphinxext`` module (#2792). The ``altair-plot`` Sphinx directive is now part of the `sphinxext-altair <https://github.com/altair-viz/sphinxext-altair>`_ package.
 
 Maintenance
 ~~~~~~~~~~~

pyproject.toml

@@ -75,6 +75,7 @@ dev = [
 doc = [
     "sphinx",
     "docutils",
+    "sphinxext_altair",
     "jinja2",
     "numpydoc",
     "pillow",