[mypyc] Make mypyc docs use the same theme as mypy docs (#10176)

Consistency is good.

Work on mypyc/mypyc#807.

Author: JukkaL

mypyc/doc/conf.py

@@ -43,8 +43,13 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-#
-html_theme = 'alabaster'
+try:
+    import sphinx_rtd_theme
+except:
+    html_theme = 'default'
+else:
+    html_theme = 'sphinx_rtd_theme'
+    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 # 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,

setup.cfg

@@ -17,6 +17,7 @@ exclude =
   .cache,
   # Sphinx configuration is irrelevant
   docs/source/conf.py,
+  mypyc/doc/conf.py,
   # conflicting styles
   misc/*,
   # conflicting styles