title: Using PySide2 on Debian causes warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome
body: <p>I have a project to do for school, using Python. I have to make a GUI, so I chose to use Qt through PySide2.
  On Windows, everything runs without problem.
  But when I try to run my project on Debian, I have this issue:</p>
  
  <pre><code>Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
  No protocol specified
  qt.qpa.xcb: could not connect to display :0
  qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
  This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
  
  Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.
  </code></pre>
  
  <p>I've searched a solution on the Internet but nothing worked for me.
  I'm using Python3.7 and PySide2 (installed with <code>pip</code>) on Debian 10.</p>