chore: explicitly request UTF-8 (for windows compatibility)

tests/param_helpers.py

@@ -23,7 +23,7 @@ def __eq__(self, other):
 def files(request, tmp_path):
     for name, contents in request.param.items():
         p = tmp_path / name
-        p.write_text(contents)
+        p.write_text(contents, encoding='utf-8')
 
     return tmp_path