% make html
…
Extension error:
Handler <function _html_page_context at 0x110466020> for event 'html-page-context' threw an exception (exception: This documentation is not using `pydoctheme.css` as the stylesheet. If you have set `html_style` in your conf.py file, remove it.)

% make html
…
                                                                                                                                                                         
Exception occurred:
  File "/Users/maciej.olko/projects/cpython/Doc/venv/lib/python3.12/site-packages/python_docs_theme/__init__.py", line 42, in _html_page_context
    raise ValueError(
    ^^^^^^^^^^^^^^^^^
ValueError: This documentation is not using `pydoctheme.css` as the stylesheet. If you have set `html_style` in your conf.py file, remove it.
The full traceback has been saved in /var/folders/c0/vxg8dn6n28105qpdxmg3kblc0000gq/T/sphinx-err-psaoa2co.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
A bug report can be filed in the tracker at <https://github.com/sphinx-doc/sphinx/issues>. Thanks!

commit 8b88430553fdaa1d7a85296a106158b5faf99a4b
Author: Hugo van Kemenade <[email protected]>
Date:   Sat Mar 11 13:32:42 2023 +0200

    Skip cache-busting for old Sphinx

diff --git a/python_docs_theme/__init__.py b/python_docs_theme/__init__.py
index 62b16f0..bbe1352 100644
--- a/python_docs_theme/__init__.py
+++ b/python_docs_theme/__init__.py
@@ -37,7 +37,7 @@ def _html_page_context(
 
     assert isinstance(app.builder, StandaloneHTMLBuilder)
 
-    if "css_files" in context:
+    if sphinx.version_info >= (4,) and "css_files" in context:
         if "_static/pydoctheme.css" not in context["css_files"]:
             raise ValueError(
                 "This documentation is not using `pydoctheme.css` as the stylesheet. "