python exceptions.UnicodeDecodeError:'ascii'编解码器无法解码字节0xa7

我正在使用scthon与python,我在python项目pipline中有这个代码

def process_item(self, item, spider):
        import pdb; pdb.set_trace()
        ID = str(uuid.uuid5(uuid.NAMESPACE_DNS, item['link']))

我收到了这个错误:

        Traceback (most recent call last):
          File "C:\Python27\lib\site-packages\scrapy-0.20.2-py2.7.egg\scrapy\mid
dleware.py", line 62, in _process_chain
            return process_chain(self.methods[methodname], obj, *args)
          File "C:\Python27\lib\site-packages\scrapy-0.20.2-py2.7.egg\scrapy\uti
ls\defer.py", line 65, in process_chain
            d.callback(input)
          File "C:\Python27\lib\site-packages\twisted\internet\defer.py", line 3
82, in callback
            self._startRunCallbacks(result)
          File "C:\Python27\lib\site-packages\twisted\internet\defer.py", line 4
90, in _startRunCallbacks
            self._runCallbacks()
        ---  ---
          File "C:\Python27\lib\site-packages\twisted\internet\defer.py", line 5
77, in _runCallbacks
            current.result = callback(current.result, *args, **kw)
          File "General_Spider_code_version_2\pipelines.py", line 7, in process_
item
            ID = str(uuid.uuid5(uuid.NAMESPACE_DNS, item['link']))
          File "C:\Python27\lib\uuid.py", line 549, in uuid5
            hash = sha1(namespace.bytes + name).digest()
        exceptions.UnicodeDecodeError: 'ascii' codec can't decode byte 0xa7 in p
osition 1: ordinal not in range(128)

我试着调试 item['link']

这就是结果

-> ID = str(uuid.uuid5(uuid.NAMESPACE_DNS, item['link']))
(Pdb) item['link']
u'http://dubai.dubizzle.com/property-for-rent/residential/apartmentflat/2014/4/6
/palm-jumeirah-abu-keibal-3-br-maid-partial-2/?back=ZHViYWkuZHViaXp6bGUuY29tL3By
b3BlcnR5LWZvci1yZW50L3Jlc2lkZW50aWFsL2FwYXJ0bWVudGZsYXQv&pos=1'
(Pdb)

如你所见,item['link']是unicode

EDIT1

当我改变item['link']任何其他属性,如item['date']代码工作完美