title: How to set a specific download location in Mozilla - Marionette web driver?
body: <p>I am having an automation script which worked well before the recent mozilla update. The selenium-python script automates some of my browser actions, and save certain reports (csv) to a defined location.</p>
  
  <p>I have been using selenium 2.53.6, which uses the following code :</p>
  
  <pre><code>profile = webdriver.firefox.firefox_profile.FirefoxProfile()
  profile.set_preference('browser.helperApps.neverAsk.saveToDisk',"text/csv, application/pdf,application/octet-stream")
  profile.set_preference('browser.download.folderList',2)
  profile.set_preference("browser.download.manager.showWhenStarting",False)
  profile.set_preference('browser.download.dir','D:\Downloads')
  driver = webdriver.Firefox(firefox_profile=profile)
  </code></pre>
  
  <p>Currently I use selenium-python 3.0.1 and Firefox 48. Here I had added the geckodriver path to environment variables and was able to launch firefox using the code below:</p>
  
  <pre><code>from selenium import webdriver
  from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
  
  caps = DesiredCapabilities.FIREFOX
  caps["marionette"] = True
  driver = webdriver.Firefox(capabilities=caps)
  </code></pre>
  
  <p>I am curious on how to do a <code>profile.set_preference</code> equivalent in firefox-marionette driver. I couldn't find any documentations on it.</p>
  
  <p>Please advise.</p>