Fix bug in "items" function (#115)

* Fix bug in "items" function

Fixes #101

* Update dict.py

Author: Sungmin-Joo

py/dict.go

@@ -29,6 +29,10 @@ var (
 
 func init() {
 	StringDictType.Dict["items"] = MustNewMethod("items", func(self Object, args Tuple) (Object, error) {
+		err := UnpackTuple(args, nil, "items", 0, 0)
+		if err != nil {
+			return nil, err
+		}
 		sMap := self.(StringDict)
 		o := make([]Object, 0, len(sMap))
 		for k, v := range sMap {

py/tests/dict.py

@@ -1,6 +1,7 @@
 # Copyright 2018 The go-python Authors.  All rights reserved.
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
+from libtest import assertRaises
 
 doc="str"
 assert str({}) == "{}"
@@ -35,6 +36,7 @@
         assert v == "b"
     if k == "c":
         assert v == 5.5
+assertRaises(TypeError, a.items, 'a')
 
 doc="__contain__"
 a = {'hello': 'world'}