updating torchvision got rid of the ImportError
2020-09-16 11:43:27  (rev 3)
     torchvision  {0.3.0 (pytorch/linux-64) -> 0.4.2 (pytorch/linux-64)}

I will keep it unsolved as: (i) maybe something might appear later on; (ii) it would be great to know how to fix/debug this in a principled manner.