Fix xml parse issue for download_bill API
Fix xml parse issue for download_bill API

hunter007/wechatpy,cloverstd/wechatpy,jxtech/wechatpy,wechatpy/wechatpy,cloverstd/wechatpy,messense/wechatpy,zaihui/wechatpy,zhaoqz/wechatpy,zaihui/wechatpy,hunter007/wechatpy,zhaoqz/wechatpy