gh-95376: Add test for names containing null (GH-GH-5394) (GH-95747)

Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@protonmail.com>
(cherry picked from commit a17cd47)

Co-authored-by: Sion Kang <31057849+Yaminyam@users.noreply.github.com>

Lib/test/test_pwd.py

@@ -59,6 +59,8 @@ def test_errors(self):
         self.assertRaises(TypeError, pwd.getpwnam)
         self.assertRaises(TypeError, pwd.getpwnam, 42)
         self.assertRaises(TypeError, pwd.getpwall, 42)
+        # embedded null character
+        self.assertRaisesRegex(ValueError, 'null', pwd.getpwnam, 'a\x00b')
 
         # try to get some errors
         bynames = {}