Merge 9f4ee6faa6 into a273bc99d2

Lib/contextlib.py

@@ -807,7 +807,12 @@ class chdir(AbstractContextManager):
         self._old_cwd = []
 
     def __enter__(self):
-        self._old_cwd.append(os.getcwd())
+        # try to chdir to the current cwd so that we preemptively fail if we are
+        # unnable to chdir back to it, see bpo-45545
+        old_cwd = os.getcwd()
+        os.chdir(old_cwd)
+
+        self._old_cwd.append(old_cwd)
         os.chdir(self.path)
 
     def __exit__(self, *excinfo):

Misc/NEWS.d/next/Library/2021-10-26-01-22-33.bpo-45545.QvsfXK.rst

@@ -0,0 +1,2 @@
+Premptively fail in :func:`contextdir.chdir` if we can't change back to the
+original directory.