Code review comment for lp:~matsubara/curtin/simplestreams

+1 to decoupling the download from the test run.

Couple of comments though:

Don't drop the checksum verification of the image; we need to keep that otherwise we can't trust the cache. If we need to be able to supply unsigned images, I think we can introduce a separate flag to disable checksums when that is needed.

It appears that the sync pulls down all images in one go, which is nice for the case where we're running the entire test suite. But if I just want to run a single test on just one release, I have to pay for all of the sync. I'd like to retain the ability to sync and run just one image.

We now have ssquery and sync data (what versions, what releases) in two places (vmtest/__init__.py and tools/vmtest-sync-images).

So, I think we need to following features:

1. a make target to pre-sync all required images
   - it needs to extract from the test cases which images and releases to pull down
     so that when we add a new test-case that requires a new release or kver or something
     this program knows that and syncs that without having to modify the source
   - images should be checksummed and the hash written out for validation on subsequent invocations.

2. ability to sync a single image based on the test-case that's being run
   - I should be able to run nosetest3 on a single test and the images should get synced if needed

3. I should be able to disable (syncing/downloading a newer image) via a flag. As you mentioned in the commit message, sometimes we don't want to sync a new image while we're debugging; in which case we want to optionally skip the sync; since this is most useful in debugging, it shouldn't be the default behavior, instead surface it through a flag.