Code review comment for lp:~julian-edwards/maas/better-error-bug-1064212

It's good to have a stopgap. Guesswork remains unpleasant, especially when we ask the user to look up information that we have at hand. After all we request information about the node from the API (see pxeconfig() in maasserver/api.py) just before it gets to this point. AFAICS that information could easily be made to include something that tells the tftp server whether the node is supposed to be netbooting right now. If we had that, we could issue a more definite "hands off, this node boots when MAAS says so" message.

The "when MAAS is not expecting that" sounds a little vague, as we're not sure ourselves what is supposed to be happening, or MAAS just felt like dozing off for a bit. Maybe "when it's not supposed to," or "when it's not in a state where MAAS allows it"?

I suppose the error could also happen if the node's state is changed in rapid succession, e.g. if it is allocated and immediately deallocated.