Only one obscure cli command uses this import, so defer the error until that command is run

@mikem Why not port this to use python-libcomps?

First things first. There is a TODO for that. I have partial work, but it's a little trickier and folks were complaining about the yum dep. Also, epel6 doesn't appear to have libcomps, so we'd probably still want to fall back to this.

@mikem It was never submitted to EPEL6, but at one point it was built for it1. If you want to move to it, it can be built and submitted to EPEL6.

Anyway, porting to libcomps is on my radar. Feel free to file an issue for it if you like :smile:, but in the meantime I'm going to pull this in soon unless there are other objections.

No objections here.

Commit 4250d9a6 fixes this pull-request