Code review comment for lp:~trapnine/maas/power-package-checks

It would definitely be cool if the drivers were pluggable instead of 'hardcoded' into MAAS. These plugins could include the client drivers, and be optional, allowing the customer to pick what they want installed.

Until then, though, I wouldn't want every power package MAAS supports installed on all my clusterd's. I may never buy AMT boxes, use virsh VM's, etc. Also, some of the power drivers (like for the IBM Power7 stuff) require privately hosted software to work, so we'd still need to check for that client software.

It seems sane to check for the real commands we're literally about to run before we attempt to do what will change power. If these commands aren't there, we tell the user what packages to install. It's not a big departure code-design-wise, and it follows the existing driver paradigm.

My only reservation with it is that it's a hard gate - there's not way to override MAAS's objection and start/commission/release, except by changing the power type or installing the desired package to make MAAS happy - maybe there should be a 'manual' power type?) Then again, the commands really won't work if clusterd can't find these binaries.