Add pyupgrade to git hooks

[ulgens]

Add pyupgrade to git hooks and apply related fixes.

Resolves #597

[coveralls]

coverage: 97.348%. remained the same — ulgens:pyupgrade into joke2k:develop

[Copilot]

Pull request overview

This PR applies pyupgrade-style modernizations intended for Python 3.9+ (per #597), primarily replacing older string formatting and updating type annotations/imports to more modern equivalents.

Changes:

• Replace str.format(...) / % formatting with f-strings across tests and packaging code.
• Simplify typing usage in environ/environ.py by removing unused typing imports and using built-in collection types in return annotations.
• Remove redundant Python 3 unicode literal prefixes (u"...") in Sphinx configuration.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/test_search.py	Converts URL construction/assertions to f-strings for readability and py39+ style.
tests/test_path.py	Updates Windows-path string expectations to f-strings.
tests/test_cache.py	Converts cache URL test strings to f-strings while preserving test intent.
setup.py	Modernizes error formatting and regex construction via f-strings / raw f-strings.
environ/environ.py	Removes unused typing imports and updates return annotations to built-in types.
docs/conf.py	Removes unnecessary u"" prefixes from string literals.

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