Make point release script compatible with docutils 0.16

scripts/release.py

@@ -141,8 +141,17 @@ def read_package(package_path: pathlib.Path) -> Package:
     return package
 
 
+def _get_docutils_parser_settings():
+    try:
+        return frontend.get_default_settings(Parser)
+    except AttributeError:
+        # docutils < 0.18. Remove fallback in 23.1
+        components = (Parser,)
+        return frontend.OptionParser(components=components).get_default_values()
+
+
 def parse_changelog(package: Package) -> List[ChangelogItem]:
-    settings = frontend.get_default_settings(Parser)
+    settings = _get_docutils_parser_settings()
     document = utils.new_document(str(package.history_rst), settings)
     Parser().parse(package.history_rst.read_text(), document)
     changelog_items: List[ChangelogItem] = []