bpo-40334: Spacialized error message for invalid args after bare '*' (GH-19865)

When parsing things like `def f(*): pass` the old parser used to output `SyntaxError: named arguments must follow bare *`, which the new parser wasn't able to do.
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 354b3f4..d83b73a 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -242,11 +242,11 @@
         check('from __future__ import doesnt_exist', 1, 1)
         check('from __future__ import braces', 1, 1)
         check('x=1\nfrom __future__ import division', 2, 1)
+        check('def f(*):\n  pass', 1, 7 if support.use_old_parser() else 8)
 
     @support.skip_if_new_parser("Pegen column offsets might be different")
     def testSyntaxErrorOffsetCustom(self):
         self.check('for 1 in []: pass', 1, 5)
-        self.check('def f(*):\n  pass', 1, 7)
         self.check('[*x for x in xs]', 1, 2)
         self.check('def f():\n  x, y: int', 2, 3)
         self.check('(yield i) = 2', 1, 1)