Verify a Python run

Every Attestable Python run returns a signed in-toto certificate (sparrow.json) that commits to the script, its resolved dependencies, and the run's output. Drop it here to check that it was really produced by an enclave the policy trusts, and to read the attested stdout and stderr.

Unlike artifact verification, the certificate is sent to our server to be checked, since it contains your run's output. To verify locally instead, run lspy verify sparrow.json.