test-execute: provide custom failure message
    
    test_exec_ambientcapabilities: exec-ambientcapabilities-nobody.service: exit status 0, expected 1
    
    Sometimes we get just the last line, for example from the failure summary,
    so make it as useful as possible.
    
    (cherry picked from commit 6aed6a11577b108b9a39f26aeae5e45d98f20c90)
    
    Related: #1737283
    
    patch_name: 0383-test-execute-provide-custom-failure-message.patch
    present_in_specfile: true
    location_in_specfile: 383
    squash_commits: true