升级到firefox到47以上版本即可
坑人的Mozilla不能起个我们熟识的名字吗？ 先是webdriver.gecko.driver后是Marionette protocol。
1、WebDriverException: Message: 'geckodriver' executable needs to be in PATH.
下载firefox驱动geckodriver可以放到python安装目录C:\Python27，http://docs.seleniumhq.org/download/
2、WebDriverException: Message: Unsupported Marionette protocol version 2, required 3
To resolve this issue you need to upgrade your
Mozilla Firefox >= v47 as well.from selenium import webdriver
import time
browser = webdriver.Firefox()
browser.get("http://www.baidu.com")
browser.find_element_by_id("kw").send_keys("selenium")
browser.find_element_by_id("su").click()
time.sleep(5)
browser.quit()
Marionette Protocol - Mozilla | MDN
https://developer.mozilla.org/en-US/docs/Mozilla/QA/Marionette/Protocol
The Marionette remote control protocol lets out-of-process programs to communicate with Gecko.
参考：
java - "org.openqa.selenium.WebDriverException: Unsupported Marionette protocol version 2" error coming while running my Selenium Script with Gecko Driver - Stack Overflow
http://*.com/questions/39729930/org-openqa-selenium-webdriverexception-unsupported-marionette-protocol-version
selenuim +python环境配置遇到的诸多问题 - 荒荒9468 - 博客园
http://www.cnblogs.com/fangfangs/p/f0000000f.html