在这个问题中，我不要求帮助解决这个问题（这个问题太多了）。我问我在哪里可以找到实际生成该错误消息的代码。
使用带有python-selenium的firefox webdriver运行时会发生错误按摩。
据我所知第一部分
WebDriverException: Message:
由硒本身产生。但是其他部分来自哪里？
TypeError: rootNode is null
它来自firefox本身吗？ geckodriver？木偶？别的什么？
我需要检查哪些源代码才能找到以下字符串？
TypeError: rootNode is null
完整的堆栈跟踪：
...
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 934, in save_screenshot
return self.get_screenshot_as_file(filename)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 911, in get_screenshot_as_file
png = self.get_screenshot_as_png()
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 943, in get_screenshot_as_png
return base64.b64decode(self.get_screenshot_as_base64().encode('ascii'))
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 953, in get_screenshot_as_base64
return self.execute(Command.SCREENSHOT)['value']
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 311, in execute
self.error_handler.check_response(response)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/errorhandler.py", line 237, in check_response
raise exception_class(message, screen, stacktrace)
WebDriverException: Message: TypeError: rootNode is null
使用的软件：