def refresh_signin_vcode(cookie, tokens, vcodetype):
url = '<STR_LIT>'.join([<EOL>const.PASSPORT_BASE,<EOL>'<STR_LIT>',<EOL>'<STR_LIT>', tokens['<STR_LIT>'],<EOL>'<STR_LIT>',<EOL>'<STR_LIT>', util.timestamp(),<EOL>'<STR_LIT>',<EOL>'<STR_LIT>', encoder.encode_uri(vcodetype),<EOL>])<EOL>headers={<EOL>'<STR_LIT>': cookie.header_output(),<EOL>'<STR_LIT>': const.REFERER,<EOL>}<EOL>logger.debug('<STR_LIT>' % url)<EOL>req = net.urlopen(url, headers=headers)<EOL>if req:<EOL><INDENT>try:<EOL><INDENT>data = req.data.decode('<STR_LIT>')<EOL>logger.debug('<STR_LIT>' % data)<EOL>return json.loads(data)<EOL><DEDENT>except ValueError:<EOL><INDENT>logger.error(traceback.format_exc())<EOL><DEDENT><DEDENT>return None<EOL>
刷新验证码.

    vcodetype - 在调用check_login()时返回的vcodetype.