PyQt5.15.2 is not compatible with debian stable (Buster)

[Ludovic Bellière]

I recently upgraded to 5.15.2 (I know, it took a while) and my project
suddenly aborted with the message:

    qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in ""
    even though it was found.

After running the project with QT_DEBUG_PLUGINS=1 (see attached log),
the culprit was found to be PyQt5/Qt/plugins/platforms/libqxcb.so,
which links to libxcb-util.so.1

libxcb-util.so.1 is from xcb 1.14, shipped with [ubuntu xenial][1],
where as [debian Buster][2] still uses xcb 1.13. xcb 1.14 is relatively
recent, roughly a year old from this message and will most likely never
be shipped in debian Buster.

As such, trying to use PyQt5.15.2 on debian Buster will fail. The last
known version to run on Buster is PyQt5.15.1. A way to resolve the
issue would be to have a dedicated build and wheel for Buster (and
other distro using the previous version of xcb), but I do not know if
it is at all possible.

Best regards,
Ludovic


[1]: https://packages.ubuntu.com/xenial/amd64/libxcb-util1/filelist
[2]: https://packages.debian.org/buster/amd64/libxcb-util0/filelist
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