bpo-45871: Refactor except matcher validation into a separate function so that it can be reused. Add missing unit test. (GH-29711)

Lib/test/test_exceptions.py

@@ -2401,6 +2401,21 @@ class SyntaxErrorTests(unittest.TestCase):
         self.assertRaises(TypeError, SyntaxError, "bad bad", args)
 
 
+class TestInvalidExceptionMatcher(unittest.TestCase):
+    def test_except_star_invalid_exception_type(self):
+        with self.assertRaises(TypeError):
+            try:
+                raise ValueError
+            except 42:
+                pass
+
+        with self.assertRaises(TypeError):
+            try:
+                raise ValueError
+            except (ValueError, 42):
+                pass
+
+
 class PEP626Tests(unittest.TestCase):
 
     def lineno_after_raise(self, f, *expected):