title: Can't open browser with Selenium after Firefox update
body: <p>I use Selenium WebDriver on Ubuntu Desktop 16.04, and I can't open browser. I get the following error after Firefox update (before this, it all worked):</p>
  
  <pre><code>Traceback (most recent call last):
    File "test.py", line 6, in &lt;module&gt;
      driver = webdriver.Firefox()
    File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/firefox/webdriver.py", line 81, in __init__
      self.binary, timeout)
    File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/firefox/extension_connection.py", line 51, in __init__
      self.binary.launch_browser(self.profile, timeout=timeout)
    File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/firefox/firefox_binary.py", line 68, in launch_browser
      self._wait_until_connectable(timeout=timeout)
    File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/firefox/firefox_binary.py", line 98, in _wait_until_connectable
      raise WebDriverException("The browser appears to have exited "
  selenium.common.exceptions.WebDriverException: Message: The browser appears to have exited before we could connect. If you specified a log_file in the FirefoxBinary constructor, check it for details.
  </code></pre>