Python 3.6版本中实现 HTMLTestRunner输出时”fp=file(filename,'wb')“报错

原错误代码：
 
if __name__=='__main__':
    suite=unittest.makeSuite(WidgetTestCase)
    filename='D:\\myreport.html'
    fp=file(filename,'wb')
    runner=HTMLTestRunner.HTMLTestRunner(fp,title=u'my unit test',description=u'This is a report test')
    runner.run(suite)
 
改成以下格式就正常了：

if __name__ == '__main__':
    filename = './myAppiumLog.html'
    with open(filename, 'wb') as f:
        # 使用HTMLTestRunner配置参数，输出报告路径、报告标题、描述
        runner = HTMLTestRunner.HTMLTestRunner(
            stream=f,
            title='Report_title',
            description='Report_description'
        )