Disallow function calls like foo(None=1).

Backport from py3k rev. 55708 by Guido.
 (backport from rev. 55802)

Lib/test/test_compile.py

@@ -37,6 +37,9 @@ class TestSpecifics(unittest.TestCase):
     def test_syntax_error(self):
         self.assertRaises(SyntaxError, compile, "1+*3", "filename", "exec")
 
+    def test_none_keyword_arg(self):
+        self.assertRaises(SyntaxError, compile, "f(None=1)", "<string>", "exec")
+
     def test_duplicate_global_local(self):
         try:
             exec 'def f(a): global a; a = 1'

Python/ast.c

@@ -1855,13 +1855,18 @@ ast_for_call(struct compiling *c, const node *n, expr_ty func)
                  * then is very confusing.
                  */
                 if (e->kind == Lambda_kind) {
-                  ast_error(CHILD(ch, 0), "lambda cannot contain assignment");
-                  return NULL;
+                    ast_error(CHILD(ch, 0),
+                              "lambda cannot contain assignment");
+                    return NULL;
                 } else if (e->kind != Name_kind) {
-                  ast_error(CHILD(ch, 0), "keyword can't be an expression");
-                  return NULL;
+                    ast_error(CHILD(ch, 0), "keyword can't be an expression");
+                    return NULL;
                 }
 		key = e->v.Name.id;
+                if (!strcmp(PyString_AS_STRING(key), "None")) {
+                    ast_error(CHILD(ch, 0), "assignment to None");
+                    return NULL;
+                }
 		e = ast_for_expr(c, CHILD(ch, 2));
                 if (!e)
                     return NULL;