[WIP] Validate hooks existence

Hmmmmm, I didn't notice that before.

0.1.0.pre comes before 0.1.0, so this PR proposes to integrate in master a version that should be released before the version that master itself targets. I see no point in doing that, the whole thing is backwards.

I may be wrong in my interpretation, but that only proves the point that bumping version in a feature branch is a bad idea.