title: WebDriverException when starting chromedriver with user-data-dir argument
body: <p>My code:</p>
  
  <pre><code>from selenium.webdriver.chrome.options import Options
  from selenium import webdriver
  opts = Options()
  opts.add_argument("user-data-dir=/path/to/profiles_dir/user_id")
  browser = webdriver.Chrome("/usr/lib/chromium-browser/chromedriver", chrome_options=opts)
  </code></pre>
  
  <p>When I start Chromium for user with id = 1 it starts fine and creates a profile directory /path/to/profiles_dir/1.
  Then I visit some arbitrary site and close the browser.
  When I execute the above code for the second time, it throws and exception.</p>
  
  <blockquote>
    <p>selenium.common.exceptions.WebDriverException: Message: unknown error: cannot parse internal JSON template: Line: 1, column: 1, Unexpected token.
      (Driver info: chromedriver=2.35.528139 (47ead77cb35ad2a9a83248b292151462a66cd881),platform=Linux 4.4.0-112-generic x86_64)</p>
  </blockquote>
  
  <ul>
  <li><p>Chromium 64.0.3282.119 Built on Ubuntu , running on Ubuntu 16.04</p></li>
  <li><p>ChromeDriver 2.35</p></li>
  <li><p>selenium 3.8.1</p></li>
  </ul>
  
  <p>I googled a lot but could not find a solution for this issue. Why can't I load the browser with the existing user profile dir? What am I doing wrong?</p>