Add missing libqxcb dependencies

[kszafran]

I run into an issue similar to #351 running pyrdp-convert.py (or pyrdp-player.py) in docker (both the latest image from dockerhub, as well as an image built locally from the Dockerfile):

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.

Aborted (core dumped)

Running with QT_DEBUG_PLUGINS I found out that libqxcb failed to load:

Cannot load library /opt/venv/lib/python3.8/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so: (libxcb-icccm.so.4: cannot open shared object file: No such file or directory)

Digging further with ldd I identified a couple of missing libraries:

ldd /opt/venv/lib/python3.8/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so | grep 'not found'
        libxcb-icccm.so.4 => not found
        libxcb-image.so.0 => not found
        libxcb-util.so.1 => not found
        libxcb-keysyms.so.1 => not found
        libxcb-randr.so.0 => not found
        libxcb-render-util.so.0 => not found

Installing these libraries with apt-get in the Dockerfile fixed the issue and I was able to produce an mp4 output. Perhaps something has changed in Ubuntu repositories.

[obilodeau]

Thanks! Will need to adjust installation instructions in the README as well.

[kszafran]

@obilodeau Thank you, I updated the README.

[obilodeau]

Thanks for the update!