Expose ExtensionError in sphinx.util for backwards compatibil…

…ity.

This will be removed in Sphinx 9, as exposing the exception
in ``sphinx.util`` was never intentional. ``ExtensionError``
has been part of ``sphinx.errors`` since v0.9.

CHANGES.rst

@@ -4,6 +4,12 @@ Release 8.1.2 (in development)
 Bugs fixed
 ----------
 
+* #13012: Expose :exc:`sphinx.errors.ExtensionError` in ``sphinx.util``
+  for backwards compatibility.
+  This will be removed in Sphinx 9, as exposing the exception
+  in ``sphinx.util`` was never intentional.
+  :exc:`!ExtensionError` has been part of ``sphinx.errors`` since Sphinx 0.9.
+  Patch by Adam Turner.
 
 Release 8.1.1 (released Oct 11, 2024)
 =====================================

sphinx/util/__init__.py

@@ -8,6 +8,7 @@
 import re
 from typing import Any
 
+from sphinx.errors import ExtensionError as _ExtensionError
 from sphinx.errors import FiletypeNotFoundError
 from sphinx.util import _files, _importer, logging
 from sphinx.util import index_entries as _index_entries
@@ -86,6 +87,7 @@ def _sha1(data: bytes = b'', **_kw: Any) -> hashlib._Hash:
         'sphinx.util.index_entries.split_into',
         (9, 0),
     ),
+    'ExtensionError': (_ExtensionError, 'sphinx.errors.ExtensionError', (9, 0)),
     'md5': (_md5, '', (9, 0)),
     'sha1': (_sha1, '', (9, 0)),
     'import_object': (_importer.import_object, '', (10, 0)),