The view function for 'search' did not return a valid response

查了一下这个报错，都说是因为有return返回了None，但是我检查了一下还是没有找到漏洞，请帮忙看一下！

# 读取表单数据，获得doc_ID
@app.route('/search/', methods=['POST'])
def search():

    try:
        global keys
        global checked
        checked = ['checked="true"', '', '']
        keys = request.form['key_word']
        #print(keys)
        if keys not in ['']:
            start_time = time.clock()

            flag,page = searchidlist(keys)
            if flag==0:   # 代表无结果，返回查询无结果的页面
                return render_template('search.html', error=False, hot_news=False)
            docs = cut_page(page, 0)

            end_time = time.clock()
            time_used = round((end_time - start_time),3)
            
            return render_template('high_search.html', checked=checked, key=keys, docs=docs, page=page,
                                   error=True, hot_news=False, time_used=time_used)
        else:
            return render_template('search.html', error=False, hot_news=False)

    except:
        print('search error')

try语句体有问题，走了except分支了吧，这样没有返回值默认为返回None，去掉try..except看具体错误
keys改成下面这样获取好点，要不名称出错会异常

keys = request.form.get('key_word',None)#['key_word']

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