fix(github): don't cache failed GitHub API responses for the full 2-h…

[chalfontchubby]

Symptom: After clearing problems with GitHub api calls for my account, present continues to complain about being unable to download GitHub version information, leading to som confusion as to the continuing problem. download_predbat_releases_url fetches the GitHub version and caches it for a 2 hour window to reduce api calls to a minimum.
However it never checked the HTTP status before treating the response body as valid data - GitHub's API returns a JSON body even on errors (e.g. rate limiting), so a 403 was parsed fine and cached as if it were real release data for 2 hours. That meant a transient rate limit kept showing "Unable to download Predbat version information" for up to 2 hours after the limit had actually cleared.

Now checks response.ok before parsing/caching, and on any failure (network error, non-2xx, bad JSON) falls back to the last successfully cached data instead of caching the failure - so the next 5-minute plan cycle retries rather than waiting out the full cache window. Also adds a request timeout, since this is an external call with no bound on how long it can hang.

[Copilot]

Pull request overview

Fixes GitHub release fetching so transient GitHub API failures (e.g., rate limiting) aren’t cached as “valid” release data for the full 2-hour cache window, and adds coverage for non-2xx responses.

Changes:

• Add response.ok checking + request timeout when fetching GitHub releases; on failures, return the last known cached data instead of caching the failure.
• Avoid updating the cache stamp/data on non-2xx or JSON failures so the next 5-minute cycle retries promptly.
• Extend test_github coverage for non-2xx responses with and without prior cached data.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
apps/predbat/github.py	Adds non-2xx guarding, timeout, and “fallback to last good cache” behavior for GitHub releases fetching.
apps/predbat/tests/test_github.py	Adds tests ensuring non-2xx responses don’t populate/refresh cache and correctly fall back to stale cached data.

[chalfontchubby]

(Hi Trefor - don't think we ever overlapped at IMG - I left in 2012 - Rik Allen. Used to run the video simulation team)