Some platforms (e.g. older macOS, exotic Linux distros) cannot build the
curl-impersonate binary that backs curl_cffi, leaving yfinance unusable.
This change keeps curl_cffi as the preferred and default backend but no
longer hard-requires it at runtime.
- New `yfinance/_http.py` abstracts the HTTP backend. If `curl_cffi` is
importable it is used as before; otherwise yfinance falls back to plain
`requests` with a realistic Chrome User-Agent and logs a warning so the
downgrade is explicit.
- `data.py`, `base.py`, `multi.py`, `scrapers/history.py` build sessions
via `_http.new_session()`.
- Scrapers and screener catch `_http.HTTPError` instead of importing
`curl_cffi.requests.exceptions.HTTPError` directly.
- `is_supported_session()` accepts either backend; `cookie_jar()` papers
over the small API difference between curl_cffi (`cookies.jar`) and
requests (`cookies` is itself the jar).
- New Advanced > Installation page documents the curl_cffi-free install
recipe; README links to it just under the install instruction.
Empirically verified that plain `requests` with a Chrome UA does not hit
the 401-after-~10-requests issue that the earlier `curl_adapter` approach
ran into; 15/15 quoteSummary calls succeed without rate limiting.
`setup.py` is unchanged -- `curl_cffi>=0.15` remains the default install
requirement (CVE-pinned). The fallback only activates when the import
fails at runtime; moving curl_cffi to extras_require can be a follow-up
decision for the maintainer.
Alessandro Colace
5d10c0c48e