Improve the "failed to download" error message

[AkihiroSuda]

Example:

images:
- location: "https://example.com/dummy-x86_64"
  arch: "x86_64"
- location: "https://example.com/dummy-aarch64"
  arch: "aarch64"

Before:

$ limactl start dummy
INFO[0000] Using the existing instance "dummy"
INFO[0000] Attempting to download the image              arch=x86_64 digest= location="https://example.com/dummy-x86_64"
FATA[0000] failed to download the image, attempted 2 candidates, errors=[failed to download "https://example.com/dummy-x86_64": expected HTTP status 200, got 404 Not Found unsupported arch: "aarch64"]

After:

$ limactl start dummy
INFO[0000] Using the existing instance "dummy"
INFO[0000] Attempting to download the image              arch=x86_64 digest= location="https://example.com/dummy-x86_64"
FATA[0000] failed to download "https://example.com/dummy-x86_64": expected HTTP status 200, got 404 Not Found

[jandubois]

This does not deal gracefully with the situation when there are no images for the required arch. I've modified the template to only have aarch64 images and tried to create an x86_64 instance:

$ l start examples/opensuse.yaml
? Creating an instance "opensuse" Proceed with the current configuration
INFO[0001] Attempting to download the nerdctl archive    arch=x86_64 digest="sha256:ce4615eb027265d2aaa61f185388738096b652541f7fc7c607bc3f829dd5713d" location="https://github.com/containerd/nerdctl/releases/download/v1.3.0/nerdctl-full-1.3.0-linux-amd64.tar.gz"
Downloading the nerdctl archive (nerdctl-full-1.3.0-linux-amd64.tar.gz)
232.92 MiB / 232.92 MiB [-----------------------------------] 100.00% 7.42 MiB/s
INFO[0033] Downloaded the nerdctl archive from "https://github.com/containerd/nerdctl/releases/download/v1.3.0/nerdctl-full-1.3.0-linux-amd64.tar.gz"
FATA[0035] exiting, status={Running:false Degraded:false Exiting:true Errors:[] SSHLocalPort:0} (hint: see "/Users/jan/.lima/opensuse/ha.stderr.log")

$ tail -1 /Users/jan/.lima/opensuse/ha.stderr.log
{"level":"fatal","msg":"open /Users/jan/.lima/opensuse/basedisk: no such file or directory","time":"2023-04-09T21:13:06-07:00"}

There is no indication that Lima didn't find an image to download at all. It should have detected this, and not proceeded to download nerdctl.

[AkihiroSuda]

Updated

[AkihiroSuda]

@jandubois PTAL

[jandubois]

Thanks, LGTM