Issue #20876: correctly close temporary file in test.support.fs_is_case_insensitive()

Lib/test/support/__init__.py

@@ -2133,7 +2133,8 @@ def skip_unless_xattr(test):
 
 def fs_is_case_insensitive(directory):
     """Detects if the file system for the specified directory is case-insensitive."""
-    base_fp, base_path = tempfile.mkstemp(dir=directory)
+    with tempfile.NamedTemporaryFile(dir=directory) as base:
+        base_path = base.name
         case_path = base_path.upper()
         if case_path == base_path:
             case_path = base_path.lower()
@@ -2141,8 +2142,6 @@ def fs_is_case_insensitive(directory):
             return os.path.samefile(base_path, case_path)
         except FileNotFoundError:
             return False
-    finally:
-        os.unlink(base_path)
 
 
 class SuppressCrashReport: