Python selenium error when trying to launch firefox

Question

I am getting an error when trying to open Firefox using Selenium in ipython notebook. I\'ve looked around and have found similar errors but nothing that exactly matches the

Answer 1

I got the same error when I set environment variable export PYTHONDONTWRITEBYTECODE=1 to get rid of pyc files on every test run. I was able to revert the change by updating selenium pip install --upgrade selenium. OSX (10.10)