gh-97930: Merge with importlib_resources 5.9 (GH-97929)

* Merge with importlib_resources 5.9

* Update changelog

Lib/importlib/resources/abc.py

@@ -1,6 +1,8 @@
 import abc
 import io
+import itertools
 import os
+import pathlib
 from typing import Any, BinaryIO, Iterable, Iterator, NoReturn, Text, Optional
 from typing import runtime_checkable, Protocol
 from typing import Union
@@ -53,6 +55,10 @@ class ResourceReader(metaclass=abc.ABCMeta):
         raise FileNotFoundError
 
 
+class TraversalError(Exception):
+    pass
+
+
 @runtime_checkable
 class Traversable(Protocol):
     """
@@ -95,7 +101,6 @@ class Traversable(Protocol):
         Return True if self is a file
         """
 
-    @abc.abstractmethod
     def joinpath(self, *descendants: StrPath) -> "Traversable":
         """
         Return Traversable resolved with any descendants applied.
@@ -104,6 +109,22 @@ class Traversable(Protocol):
         and each may contain multiple levels separated by
         ``posixpath.sep`` (``/``).
         """
+        if not descendants:
+            return self
+        names = itertools.chain.from_iterable(
+            path.parts for path in map(pathlib.PurePosixPath, descendants)
+        )
+        target = next(names)
+        matches = (
+            traversable for traversable in self.iterdir() if traversable.name == target
+        )
+        try:
+            match = next(matches)
+        except StopIteration:
+            raise TraversalError(
+                "Target not found during traversal.", target, list(names)
+            )
+        return match.joinpath(*names)
 
     def __truediv__(self, child: StrPath) -> "Traversable":
         """