There is a problem that Selenium is monitoring that it is blocked. A puppet problem .
Since the problem is for 3 weeks, and looking at their fixation log , I would not hold my breath for the patch in the near future.
If you can use Firefox 47.0.1 because they had a different error in Firefox 47.0 , you can use the old WebDriver API, which works (not a puppet). From 48 it stops working because you have to use Marionette. Yes, this puppet is not finished yet.
If you have to test Firefox, I recommend that you stick with Firefox 47.0.1, Selenium 2.latest, ultimately throw them in the docker image and run like this.
What I am doing, at least for the Germanium , until he, hopefully, will eventually work for the Marionette as well.
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