Fiddler- Receive Failure

[keycxl]

利用python写了个爬虫程序爬网页，打开fiddler出现：
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已经抓取: 0 正在抓取 <--- http://www.baidu.com
Traceback (most recent call last):
File "C:\Users\15514\Desktop\Python网络爬虫Ver 1.0 alpha.py", line 21, in <module>
urlop = urllib.request.urlopen(url)
File "C:\Python34\lib\urllib\request.py", line 161, in urlopen
return opener.open(url, data, timeout)
File "C:\Python34\lib\urllib\request.py", line 469, in open
response = meth(req, response)
File "C:\Python34\lib\urllib\request.py", line 579, in http_response
'http', request, response, code, msg, hdrs)
File "C:\Python34\lib\urllib\request.py", line 507, in error
return self._call_chain(*args)
File "C:\Python34\lib\urllib\request.py", line 441, in _call_chain
result = func(*args)
File "C:\Python34\lib\urllib\request.py", line 587, in http_error_default
raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 504: Fiddler - Receive Failure

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但是关闭fiddler是正常的，求解？？？