FAIL：TypeError：异常必须是旧式类或派生自BaseException，而不是unicode Robotframework

Question

当我尝试运行Appium RobotframeWork时，我遇到了错误

我的示例代码：

*** Settings ***
Library           AppiumLibrary

     Test Cases
        AB
        Open Application 
        ...    http://localhost:4723/wd/hub
        ...    platformName=Android
        ...    platformVersion=8.0.0
        ...    deviceName=emulator-5554
        ...    appPackage=com.grabqpons.android
        ...    appActivity=com.grabqpons.android.MainActivity

        Sleep    2s
        Click Button    xpath=//*[startswith(@id,'slide-skip-btn')]
        Sleep    2s

响应：

**Starting test: Sai.AB**

20180118 16:30:17.961 :  INFO : Slept 2 seconds
20180118 16:30:19.276 :  INFO : </td></tr><tr><td colspan="3">
<a href="appium-screenshot-1.png"><img src="appium-screenshot-1.png" width="800px"></a>
20180118 16:30:19.277 :  FAIL : TypeError: exceptions must be old-style 
classes or derived from BaseException, not unicode
Ending test:   Sai.AB