Consider using a python lib to manipulate partition tables

[ydirson]

We currently parse the output of programs clearly not meant for being parsed. A python lib instead, like python-parted, would give us structured information and would avoid problems such as the one fixed in the PR referenced below.

Originally posted in #207 (comment)

[MarkSymsCtx]

That does then add additional, currently unsatisfied, dependencies which would need to be built and maintained.