! exec karma --check-config
! stdout .
cmp stderr stderr.txt

-- stderr.txt --
level=ERROR msg="Execution failed" error="failed to unmarshal configuration: decoding failed due to the following error(s):\n\n'Silences.Expired' time: invalid duration"
-- karma.yaml --
alertmanager:
  servers:
    - name: default
      uri: https://127.0.0.1:9093
silences:
  expired: abc
