Fixed watch server tests on Windows

[david-yz-liu]

Proposed Changes

(Describe your changes here. Also describe the motivation for your changes: what problem do they solve, or how do they improve the application or codebase? If this pull request fixes an open issue, use a keyword to link this pull request to the issue.)

This PR fixes two tests in test_check.py (test_check_watch_enabled, test_watch_output_file_appends) that were failing on Windows. There are three fixes:

1. On Windows, select.select only support sockets and not pipe file objects like process.stdout/process.stderr. The tests were switched to using daemon threads to read from the process streams and write to a queue.
2. reset_watch_fixture()/modify_watch_fixture() build a throwaway Python script by embedding a raw path into an f-string: output="{output_path}". On Windows, paths contain backslashes (e.g. C:\Users\... which were SyntaxErrors in the script. This was fixed by using repr() to escape the path: output={output_path!r}.
3. On Windows, when stdout is redirected/piped, Python defaults to the system codebase (e.g. cp1252). This failed to encode characters like ‾, which the PlainReporter uses to underline parts of the error message. This was fixed by setting the output stream encoding to UTF-8 across all reporters.

Screenshots of your changes (if applicable)

Type of Change

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Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
🐛 Bug fix (non-breaking change that fixes an issue)	X
♻️ Refactoring (internal change to codebase, without changing functionality)
🚦 Test update (change that only adds or modifies tests)	X
📚 Documentation update (change that only updates documentation)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

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[coveralls]

Coverage Report for CI Build 35550437941

Coverage increased (+0.004%) to 90.882%

Details

• Coverage increased (+0.004%) from the base build.
• Patch coverage: 2 of 2 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	4091
Covered Lines:	3718
Line Coverage:	90.88%
Coverage Strength:	17.66 hits per line

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💛 - Coveralls