title: Unable to open X display with python subprocess and DISPLAY and XAUTHORITY variables set
body: <p>I'm trying to launch a message box from a python systemd service which is running as root. </p>
  
  <pre><code>subprocess.Popen(["/usr/bin/zenity", "--info", "--text", "please reboot for changes to take effect"], env=dict(os.environ, DISPLAY="0.0", XAUTHORITY="/home/pi/.Xauthority"))
  </code></pre>
  
  <p>I've set the environment variable DISPLAY and XAUTHORITY however I still get a connection refused message</p>
  
  <pre><code>** (zenity:5491): WARNING **: Could not open X display
  Unable to init sever: Could not connect: Connection refused
  (zenity:5491): Gtk-WARNING **: cannot open display: 0.0
  </code></pre>
  
  <p>Is there anything I'm missing here?</p>