Comment 6 for bug 1473517

@Mario

Turns out my idea to go via 1.21 is flawed - it can result in errors because 1.21 does not recognise wily.

We are about to release a 1.22.7 which will fix the underlying upgrade issue so you can go straight from 1.20 to 1.22.7 in one step.
I hope to have that in a proposed ppa within a day and then stable next week.