when I can't delete FF cookies from webdriver. When I use the .delete_all_cookies method, it returns None. And when I try to get_cookies, I get the following error:
webdriver_common.exceptions.ErrorInResponseException: Error occurred when processing
packet:Content-Length: 120
{"elementId": "null", "context": "{9b44672f-d547-43a8-a01e-a504e617cfc1}", "parameters": [], "commandName": "getCookie"}
response:Length: 266
{"commandName":"getCookie","isError":true,"response":{"lineNumber":576,"message":"Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMLocation.host]","name":"NS_ERROR_FAILURE"},"elementId":"null","context":"{9b44672f-d547-43a8-a01e-a504e617cfc1} "}
How can I fix it?
Update:
This happens with clean installation of webdriver with no modifications. The changes I've mentioned in another post were made later than this post being posted (I was trying to fix the issue myself).
Hmm, I actually haven't worked with Webdriver so this may be of no help at all... but in your other post you mention that you're experimenting with modifying the delete cookie webdriver js function. Did get_cookies fail before you were modifying the delete function? What happens when you get cookies before deleting them? I would guess that the modification you're making to the delete function in webdriver-read-only\firefox\src\extension\components\firefoxDriver.js could break the delete function. Are you doing it just for debugging or do you actually want the browser itself to show a pop up when the driver tells it to delete cookies? It wouldn't surprise me if this modification broke.
My real advice though would be actually to start using Selenium instead of Webdriver since it's being discontinued in it's current incarnation, or morphed into Selenium. Selenium is  more actively developed and has pretty active and responsive forms. It will continue to be developed and stable while the merge is happening, while I take it Webdriver might not have as many bugfixes going forward. I've had success using the Selenium commands that control cookies. They seem to be revamping their documentation and for some reason there isn't any link to the Python API, but if you download selenium rc, you can find the Python API doc in selenium-client-driver-python, you'll see there are a good 5 or so useful methods for controlling cookies, which you use in your own custom Python methods if you want to, say, delete all the cookies with a name matching a certain regexp. If for some reason you do want the browser to alert() some info about the deleted cookies too, you could do that by getting the cookie names/values from the python method, and then passing them to selenium's getEval() statement which will execute arbitrary js you feed it (like "alert()"). ... If you do go the selenium route feel free to contact me if you get a blocker, I might be able to assist.
How to delete Firefox cookies from webdriver in python?