chore: avoid masking errors in docker validation script

[mpeddada1]

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Fixes #<issue_number_goes_here> ☕️

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[mpeddada1]

After adding set -o pipefail, the script is failing with the following error, as expected:

ERROR: (gcloud.container.images.describe) [gcr.io/cloud-devrel-public-resources/graalvm_a:1.6.0] is not a valid name. Expected tag in the form "base:tag" or "tag" or digest in the form "sha256:<digest>"
+ exit_status=1
+ [[ 1 = 0 ]]
+ exit 1
cleanup

[lqiu96]

Wouldn't set -o pipefail exit with the non-zero status code? I might be missing something, but Is this check needed?

[mpeddada1]

That's a good question! Just tried it out in f48fb2d but unfortunately, it looks like we still need the check otherwise the script results in an exit 0 even when the command results in an error:

ERROR: (gcloud.container.images.describe) [:latest] digest must be of the form "sha256:<digest>".
+ exit_status=1
cleanup

[ID: 8899040] Command finished after 23 secs, exit value: 0