Selenium, python and Firefox 22

Problem
Selenium refuses to work with Firefox22 although it works properly with Firefox21. A lot of posts poured over internet. Example :
https://groups.google.com/forum/#!topic/selenium-users/1psXxdH-zS0
Although there is a fix available for Selenium 2.22 it seems not working for python users.
My solution
By I find a way to force Selenium to use Firefox21 without removing Firefox22.

• Download and install somewhere Firefox21 (for instance /home/opt/firefox21/firefox)
• Force selenium starter to use it by adding browserConfigurationOptions parameter to start method. 

selenium = selenium(host, port, browser, http)
selenium.start(("executablePath=/home/opt/firefox21/firefox"))