hydra-queue-runner is more anal about the format than Catalyst, so it was misinterpreting gc_roots_dir.
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using_frontend_proxy 1
base_uri ${cfg.hydraURL}
notification_sender ${cfg.notificationSender}
max_servers 25
compress_num_threads 0
using_frontend_proxy = 1
base_uri = ${cfg.hydraURL}
notification_sender = ${cfg.notificationSender}
max_servers = 25
compress_num_threads = 0