sherlock: gate errorType message on HTTP status (fixes #2950)

[SkxOverKill]

Summary

Fixes #2950 — minds (and every other errorType: "message" site) reported usernames as Claimed when the upstream returned a transient 5xx (e.g. HTTP 502 from the register/validate API) whose body lacked the configured errorMsg.

Root cause

In sherlock_project/sherlock.py, the errorType == "message" branch only did a substring check for errorMsg in the response body. Any non-2xx response without the error message fell through to QueryStatus.CLAIMED.

Changes

• sherlock_project/sherlock.py: in the message branch, only report CLAIMED for healthy 200..299 responses when the error message is absent; non-2xx responses are downgraded to UNKNOWN.
• tests/test_probes.py: new offline regression test (monkeypatches away the HTTP layer) asserting:
  • 502 + body without errorMsg → UNKNOWN (was CLAIMED),
  • 200 + body with errorMsg → AVAILABLE,
  • 200 + body without errorMsg → CLAIMED.

Verification

• pytest tests/test_probes.py -m "not online" passes (2 passed).
• Full offline suite remains green (the only pre-existing failures are environment-related py -m subprocess tests that also fail on master).