使用appium进行remove_app或者install_app操作报错

求帮助！我大概能知道是进程的原因，但仍然是百思不得其解！使用appium进行remove_app或者install_app操作报错Message: ERROR running Appium command: Cannot read property 'curDeviceId' of null

desired_caps = {
                'platformName': 'Android',
                'deviceName': 'Z2X4C15723003439',
                # 'deviceName': 'LE67A06230436549',
                'platformVersion': '6',
                # 'app': packages[0]
                # apk包名
                 'appPackage': 'com.cehome.tiebaobei',
                # apk的launcherActivity
                'appActivity': 'com.cehome.tiebaobei.activity.MainEntranceActivity'
                }
driver = webdriver.Remote('http://127.0.0.1:4723/wd/hub',desired_caps)
time.sleep(20)
driver.close_app()
time.sleep(30)
driver.remove_app('com.cehome.tiebaobei')