Docs: use Node.findall to avoid a deprecation warning (GH-99403)

(cherry picked from commit 1e9dfda)

Co-authored-by: Adam Turner <[email protected]>

Author: miss-islington

Doc/tools/extensions/c_annotations.py

@@ -20,6 +20,7 @@
 """
 
 from os import path
+import docutils
 from docutils import nodes
 from docutils.parsers.rst import directives
 from docutils.parsers.rst import Directive
@@ -41,6 +42,16 @@
 }
 
 
+# Monkeypatch nodes.Node.findall for forwards compatability
+# This patch can be dropped when the minimum Sphinx version is 4.4.0
+# or the minimum Docutils version is 0.18.1.
+if docutils.__version_info__ < (0, 18, 1):
+    def findall(self, *args, **kwargs):
+        return iter(self.traverse(*args, **kwargs))
+
+    nodes.Node.findall = findall
+
+
 class RCEntry:
     def __init__(self, name):
         self.name = name
@@ -87,7 +98,7 @@ def __init__(self, refcount_filename, stable_abi_file):
                 self.stable_abi_data[name] = record
 
     def add_annotations(self, app, doctree):
-        for node in doctree.traverse(addnodes.desc_content):
+        for node in doctree.findall(addnodes.desc_content):
             par = node.parent
             if par['domain'] != 'c':
                 continue