【Selenium】【BugList7】执行driver.find_element_by_id("kw").send_keys("Selenium")，报错：selenium.common.exceptions.InvalidArgumentException: Message: Expected [object Undefined] undefined to be a string

【版本】

selenium：3.11.0

firefox：59.0.3 (64 位)

python：3.6.5

【代码】

 #coding=utf-8
 from selenium import webdriver

 driver = webdriver.Firefox()
 driver.get("http://www.baidu.com")

 driver.find_element_by_id("kw").send_keys("Selenium")
 driver.find_element_by_id("su").click()
 driver.quit()

【报错】

==================== RESTART: E:/python_work/1 firefox.py ====================
Traceback (most recent call last):
File "E:/python_work/1 firefox.py", line 7, in <module>
driver.find_element_by_id("kw").send_keys("Selenium")
File "D:\Program Files\Python36\lib\site-packages\selenium\webdriver\remote\webelement.py", line 479, in send_keys
'value': keys_to_typing(value)})
File "D:\Program Files\Python36\lib\site-packages\selenium\webdriver\remote\webelement.py", line 628, in _execute
return self._parent.execute(command, params)
File "D:\Program Files\Python36\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 312, in execute
self.error_handler.check_response(response)
File "D:\Program Files\Python36\lib\site-packages\selenium\webdriver\remote\errorhandler.py", line 242, in check_response
raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.InvalidArgumentException: Message: Expected [object Undefined] undefined to be a string

【解决方法】

升级geckodriver到v0.21.0已解决：https://github.com/mozilla/geckodriver/releases