Issue#2238: some syntax errors from *args or **kwargs expressions
would give bogus error messages, because of untested exceptions::

    >>> f(**g(1=2))
    XXX undetected error
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: 'int' object is not iterable

instead of the expected SyntaxError: keyword can't be an expression

Will backport.
diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index e2bb3eb..0e59367 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -282,6 +282,10 @@
         def d32v((x,)): pass
         d32v((1,))
 
+        # Check ast errors in *args and *kwargs
+        check_syntax_error(self, "f(*g(1=2))")
+        check_syntax_error(self, "f(**g(1=2))")
+
     def testLambdef(self):
         ### lambdef: 'lambda' [varargslist] ':' test
         l1 = lambda : 0