gh-121200: Log pwd entry in test_expanduser_pwd2() (#121207)

Use subTest() to log the pwd entry in test_expanduser_pwd2() of
test_posixpath to help debugging.

Author: vstinner

Lib/test/test_posixpath.py

@@ -359,13 +359,14 @@ def test_expanduser_pwd(self):
                      "no home directory on VxWorks")
     def test_expanduser_pwd2(self):
         pwd = import_helper.import_module('pwd')
-        for e in pwd.getpwall():
-            name = e.pw_name
-            home = e.pw_dir
+        for entry in pwd.getpwall():
+            name = entry.pw_name
+            home = entry.pw_dir
             home = home.rstrip('/') or '/'
-            self.assertEqual(posixpath.expanduser('~' + name), home)
-            self.assertEqual(posixpath.expanduser(os.fsencode('~' + name)),
-                             os.fsencode(home))
+            with self.subTest(pwd=entry):
+                self.assertEqual(posixpath.expanduser('~' + name), home)
+                self.assertEqual(posixpath.expanduser(os.fsencode('~' + name)),
+                                 os.fsencode(home))
 
     NORMPATH_CASES = [
         ("", "."),