Add compat.py39.LOCALE_ENCODING

Author: abravalheri

setuptools/compat/py39.py

@@ -0,0 +1,9 @@
+import sys
+
+# Explicitly use the ``"locale"`` encoding in versions that support it,
+# otherwise just rely on the implicit handling of ``encoding=None``.
+# Since all platforms that support ``EncodingWarning`` also support
+# ``encoding="locale"``, this can be used to suppress the warning.
+# However, please try to use UTF-8 when possible
+# (.pth files are the notorious exception: python/cpython#77102, pypa/setuptools#3937).
+LOCALE_ENCODING = "locale" if sys.version_info >= (3, 10) else None