Integration CI fails to run with firefox snap on the ubuntu platform

[Hua Zhang]

Sometimes we need to set up a local integration CI test env for debugging purposes. However, I hit this error 'selenium.common.exceptions.InvalidArgumentException: Message: binary is not a Firefox executable' while running 'tox -e integration' [1] locally on the ubuntu platform.

Upon investigation, I found that the root cause was because I had installed firefox via snap rather debian package. Specifying firefox_bin="/snap/firefox/current/usr/lib/firefox/firefox" for selenium's WebDriver can fix the problem [2].

I also checked horzion code, although firefox_binary.py#WebDriver[3] introduced the firefox_binary parameter, but the code calling it did not pass firefox_binary to it, nor did it pass firefox_binary to selenium's WebDriver.

[1] https://docs.openstack.org/horizon/latest/contributor/testing.html
[2] https://github.com/SeleniumHQ/selenium/issues/13252
[3] https://github.com/openstack/horizon/blob/master/horizon/test/firefox_binary.py#L71