Failed save code now request reported as succeded

A save code now request for a non existent GitHub repository (https://github.com/FrictionalGames/AmnesiaMachineForPigs) is reported as "succeeded" in the dashboard, while the status found in the Tasklog is "failed"

[2020-10-02 15:39:53,928: INFO/ForkPoolWorker-1666] Task swh.loader.git.tasks.UpdateGitRepository[c1e8f91a-ae22-472d-9ce6-ba937f7eb9a1] succeeded in 0.8637380450963974s: {'status': 'failed'}

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Migrated from T2658 (view on Phabricator)