Date a bug's age from old tags via raw.githubusercontent, no API quota

When old wheels won't install (no builds for any Python you have), you can still bound how long a bug lived by reading the source at old release tags. Fetch https://raw.githubusercontent.com/<org>/<repo>/<tag>/<path> with curl. This doesn't count against the 60/h unauthenticated REST quota, and you don't need a clone. Then grep for the buggy expression. Examples: scikit-learn BayesianRidge.predict at tag 0.19.0 centres X only when normalize=True, so the return_std bug dates from when the option was added. statsmodels varfuncs.Binomial.deriv returns '1 - 2*mu' at v0.8.0 (and has no deriv at v0.5.0). Tag names differ by repo ('0.19.0' vs 'v0.8.0'), and files move between releases, so a 404 means check the path, not that the code is absent. State in your write-up that these versions rest on reading the source, not on execution.