The test was failing because nix path-info --json now returns narHash as
a structured dictionary {"algorithm": "sha256", "format": "base64",
"hash": "..."} instead of an SRI string "sha256-...".
This change was introduced in commit 5e7ee808d. The functional test
path-info.sh was updated at that time, but this NixOS test was missed.
The fix converts the dictionary format to SRI format inline:
tarball_hash_sri = f"{narHash_obj['algorithm']}-{narHash_obj['hash']}"
53af1119fb