The symbolication log could not distinguish a healthy run from one where every
symbol fetch failed. Two causes:
- symbolicate_modules counted every entry as "frames resolved", including the
<unsymbolicated> fallbacks, so a run that resolved nothing looked identical to
a full one. It now reports resolved and unsymbolicated counts separately and
warns when unsymbolicated frames outnumber resolved ones.
- fetch_url swallowed every OSError silently, so a systemic network, TLS, or
proxy failure left no trace. It now logs the failure once per exception type
(naming the cause) while staying quiet about the expected 404s for OS
libraries that have no symbols on the server.
Logging only; the fetch, parse, and aggregation results are unchanged.
Differential Revision: https://phabricator.services.mozilla.com/D311903
Sky Ning
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