Specify utf-8 encoding when reading module source files (#329)

* Specify utf-8 encoding when reading module source files

Avoids reliance on the platform default locale when parsing
imported module sources for matter base test class detection.

Fixes #323

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* Use Path.read_text instead of nested with-open block

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: oxesoft

test_collections/matter/sdk_tests/support/python_testing/list_python_tests_classes.py

@@ -225,8 +225,9 @@ def _is_matter_base_test_class(
                 try:
                     abs_path = str(candidate.resolve())
                     if abs_path not in _module_cache:
-                        with open(candidate, "r") as f:
-                            _module_cache[abs_path] = ast.parse(f.read())
+                        _module_cache[abs_path] = ast.parse(
+                            candidate.read_text(encoding="utf-8")
+                        )
                     imported_module = _module_cache[abs_path]
 
                     # Use the absolute path as the cycle-guard key so that