pytest get_screenshot_as_file报错

请问使用pytest时，截图功能get_screenshot_as_file报错，是什么原因啊，平时用没问题，在pytest执行就报错

import pytest
from selenium import webdriver
from selenium.webdriver.common.by import By
from time import sleep
from PIL import Image
class Test_错误登录:

    def test_1(self):
        print('\n用例1')
        driver=webdriver.Chrome()
        driver.implicitly_wait(10)
        driver.get('http://127.0.0.1/mgr/sign.html')
        # driver.find_element(By.ID,'username').send_keys('')
        driver.find_element(By.ID,'password').send_keys('88888888')
        driver.find_element(By.TAG_NAME,'button').click()
        sleep(2)
        driver.get_screenshot_as_file(r'D:\1.png')
        alertText = driver.switch_to.alert.text
        print(alertText)
        assert alertText =='请输入用户名'
        sleep(2)
        driver.quit()

本身截图函数没有问题啊，你这报错提示是系统找不到文件吧