Old non-square EKOs can no longer be loaded

[Radonirinaunimi]

This is what I mentioned yesterday and I am not sure if there is anything that can be done in this respect. As far as pineko is concerned, this is the only stopover (at the level of the test) in order to use v0.15 EKOs. The PineAPPL Python API works fine with v0.15 EKOs already.

[Radonirinaunimi]

The other obvious option is of course to update all of the old EKOs used in the regression tests. But you know...