What do these changes do?

This PR fixes a regression I introduced when vendoring SimpleCookie - I accidentally copied the wrong _unquote function. The correct implementation from Python's http.cookies module is now vendored, which properly handles:

• Octal escape sequences in cookie values (e.g., \012 for newline, \011 for tab)
• Escaped quotes (\") and backslashes (\\)
• All edge cases that the standard library handles

Comprehensive tests have been added to ensure the vendored function behaves identically to SimpleCookie's implementation.

Are there changes in behavior for the user?

Cookie parsing will now correctly handle cookies with octal escape sequences in their values, restoring compatibility with servers that send such cookies. This fixes a regression where these cookies were not being decoded properly.

Is it a substantial burden for the maintainers to support this?

No. This is a straightforward vendoring of a stable function from Python's standard library that has remained unchanged for years. The implementation is well-tested and matches Python's cookie handling behavior exactly. The comprehensive test suite ensures any future changes will be caught.

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
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    Fixed issue with non-ascii contents in doctest text files
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