OpenGL version is hard-coded to 2.0

[TLATER]

I'm trying to create a flatpak for webmacs (see this branch for a sneak-peek), but when running this with all dependencies installed I run into the following problem:

Attribute Qt::AA_ShareOpenGLContexts must be set before QCoreApplication is created.
Traceback (most recent call last):
  File "/app/bin/webmacs", line 11, in <module>
    load_entry_point('webmacs==0.7', 'console_scripts', 'webmacs')()
  File "/app/lib/python3.7/site-packages/webmacs/main.py", line 253, in main
    else "webmacs-%s" % opts.instance
  File "/app/lib/python3.7/site-packages/webmacs/application.py", line 109, in __init__
    if (version.opengl_vendor() == 'nouveau' and
  File "/app/lib/python3.7/site-packages/webmacs/version.py", line 71, in opengl_vendor
    vf = ctx.versionFunctions(vp)
ModuleNotFoundError: No module named 'PyQt5._QOpenGLFunctions_2_0'

It appears that the kde platform only supports OpenGL 2.2+, or at the very least it does not support 2.0 (I haven't been able to pinpoint exactly which modules do exist, although hard-coding 2.2 does work).

Currently, the OpenGL version used by webmacs is hard-coded, so it's impossible to launch webmacs with the default flatpak runtime (or on any other system with slightly fewer dependencies).

Is there anything we could do here other than hard-coding version 2.0?