`ResponseFactory.__extract_browser_encoding` matched the charset with
`charset=([\w-]+)`, which stops at a quote character. RFC 7231 permits the
charset value to be a quoted-string (e.g. `content-type: text/html;
charset="ISO-8859-1"`), so for any quoted charset the regex failed to match
and the function silently fell back to the `utf-8` default. A page served as
quoted ISO-8859-1 / windows-1252 / Shift_JIS would then be decoded as UTF-8,
producing mojibake.
Allow an optional surrounding quote in the pattern (`charset=["']?([\w-]+)`)
so the value is captured without the quote. Unquoted headers are unaffected.
The existing `content_type_map` fixture in tests/fetchers/test_utils.py was
unused; add focused tests covering unquoted, quoted, and missing charsets.
Bortlesboat
6390c0af3d