Why upgrading CubicWeb minimum version? We don't support 3.25 and
less, and even 3.26 should disappear but it is the last version
that supports Python 2 and it is in consequence sadly still used.
So it is better not to create illusion and be clear that we won't
add a fix for a too old version of CubicWeb. Projects must
upgrade, maintaining very old stuff is dirty work.