Raring’s selenium doesn’t like Raring’s Firefox. My solution: uninstall python-selenium in the system (if you need your virtualenv to have access to system packages, as I do), make a virtualenv, and run pip install selenium after activating the virtualenv (source bin/activate).

The symptom is that tests fail with the following.

WebDriverException: Message: ‘Can\’t load the profile. Profile Dir: /tmp/tmpAmYXPX Firefox output: \n(process:8197): GLib-CRITICAL **: g_slice_set_config: assertion `sys_page_size == 0\’ failed\nXlib: extension “RANDR” missing on display “:1431”.\n*** LOG addons.xpi: startup\n*** LOG addons.xpi: checkForChanges\n*** LOG addons.xpi: No changes found\n’