代码：
driver.switch_to.alert.accept()
报错：
Exception:
org.openqa.selenium.UnsupportedCommandException: Invalid Command Method - Request => {"headers":{...},"httpVersion":"1.1","method":"GET","url":"/alert_text","urlParsed":{...},"urlOriginal":"/session/13ddee20-110f-11e3-af52-a75f21929065/alert_text"}
在网上找了很多种方法，一直无解；
https://github.com/detro/ghostdriver/issues/20
论坛讨论详情；