Pipeline should fail when a user does not exist

[pi-vikassaroha]

Current behaviour

We see that using this repo, the build is marked as successful when a user doesn't exist in Buildkite. The diff step identifies the file changes but does not trigger the next step (pipeline). This behaviour leads to green build status even though the triggers didn't run.

expected behaviour

If the trigger is unable to be started as a result of users account not existing in Buildkite, the build step should raise this as a failure.