title: Selenium 'Unable to find matching set of capabilites error'
body: <p>When running my Python script which uses Selenium I get this error. Any ideas on how to fix it?</p>
  
  <pre><code>File "mypythonscript.py", line 136, in main
      driver = webdriver.Firefox(profile)
    File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/firefox/webdriver.py", line 152, in __init__
      keep_alive=True)
    File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 98, in __init__
      self.start_session(desired_capabilities, browser_profile)
    File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 188, in start_session
      response = self.execute(Command.NEW_SESSION, parameters)
    File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 252, in execute
      self.error_handler.check_response(response)
    File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/errorhandler.py", line 194, in check_response
      raise exception_class(message, screen, stacktrace)
  selenium.common.exceptions.WebDriverException: Message: Unable to find a matching set of capabilities
  </code></pre>