The python-gdal package was failing to build with the updated gdal (and
therefore qgis too), but I was able to fix the issue by building the
Python bindings directly in the gdal package (commit
25f702449c8683b3ec78b2e4a5728e700462e5a2).
Patch pushed as d8231432c57a3d8d8def39c2effd45221794bb6f.
Thanks.