api_test.py test in ubuntu_lxc failed on non amd64 / arm64

[Po-Hsu Lin]

In cycle s2023.06.12, the api_test.py in ubuntu_lxc is now failing on s390x and PowerPC with:
"ERROR: Couldn't find a matching image."

Test log:
     START ubuntu_lxc.api_test.py ubuntu_lxc.api_test.py timestamp=1689308475 timeout=1200 localtime=Jul 14 00:21:15
 Persistent state client._record_indent now set to 2
 Persistent state client.unexpected_reboot now set to ('ubuntu_lxc.api_test.py', 'ubuntu_lxc.api_test.py')
 Waiting for pid 20535 for 1200 seconds
 Running 'python3 /usr/share/doc/python3-lxc/examples/api_test.py'
 The cached copy has expired, re-downloading...
 Setting up the GPG keyring
 Downloading the image index
 ERROR: Couldn't find a matching image.
 Getting instance for 'df8a4aa0-21fd-11ee-b77f-02290a000007'
 Creating rootfs using 'download', arch=s390x
 Traceback (most recent call last):
   File "/usr/share/doc/python3-lxc/examples/api_test.py", line 72, in
     assert(container.defined)
 AssertionError

If you run the `sudo lxc-create -t download -n apitest` on a Xenial s390x instance, the only available ubuntu instances will be:
ubuntu bionic amd64 default 20230717_07:43
ubuntu bionic arm64 default 20230717_07:43
ubuntu focal amd64 default 20230717_07:43
ubuntu focal arm64 default 20230717_07:43
ubuntu jammy amd64 default 20230717_08:49
ubuntu jammy arm64 default 20230717_07:43
ubuntu lunar amd64 default 20230717_07:43
ubuntu lunar arm64 default 20230717_07:43
ubuntu mantic amd64 default 20230717_07:43
ubuntu mantic arm64 default 20230717_07:43
ubuntu xenial amd64 default 20230717_08:49
ubuntu xenial arm64 default 20230717_07:43

Looks like the s390x and ppc64el are gone.

[Po-Hsu Lin (cypressyew)]

The available list can be found here as well: https://images.linuxcontainers.org/