def get_signin_vcode(cookie, codeString):
url = '<STR_LIT>'.join([<EOL>const.PASSPORT_BASE,<EOL>'<STR_LIT>',<EOL>codeString,<EOL>])<EOL>headers={<EOL>'<STR_LIT>': cookie.header_output(),<EOL>'<STR_LIT>': const.REFERER,<EOL>}<EOL>req = net.urlopen(url, headers=headers)<EOL>if req:<EOL><INDENT>return req.data<EOL><DEDENT>else:<EOL><INDENT>return None<EOL><DEDENT>
获取登录时的验证码图片.

    codeString - 调用check_login()时返回的codeString.