[TINGyu123644]

Why are these changes needed?

python/docs/redirects/redirects.py reads the redirect template, writes the generated redirect index.html pages, and reads the redirect URL list without specifying an explicit encoding. On Windows locales where Python's default encoding is not UTF-8, this can raise UnicodeDecodeError / UnicodeEncodeError when those files contain non-ASCII characters. Fixes #7749.

This is an AI-assisted documentation-tooling fix.

Related issue number

Fixes #7749

Checks

• Doc changes included (this script generates the documentation redirect pages).
• Tests added — not applicable; the script has no test suite and the change only adds encoding="utf-8" to three open() calls.
• Verified with python -m py_compile that the edited script still compiles.

Behavior is unchanged for ASCII content and is now safe for non-ASCII files on systems whose default encoding is not UTF-8.