WIP: more windoes shenanigans

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

Author: jku

tests/test_updater_top_level_update.py

@@ -712,7 +712,7 @@ def test_load_metadata_from_cache(self, wrapped_open: MagicMock) -> None:
         root_dir = os.path.join(self.metadata_dir, "root_history")
         wrapped_open.assert_has_calls(
             [
-                call(os.path.join(self.metadata_dir, ".lock"), "x+b"),
+                call(os.path.join(self.metadata_dir, ".lock"), "a+"),
                 call(os.path.join(root_dir, "2.root.json"), "rb"),
                 call(os.path.join(self.metadata_dir, "timestamp.json"), "rb"),
                 call(os.path.join(self.metadata_dir, "snapshot.json"), "rb"),

tuf/ngclient/updater.py

@@ -89,7 +89,7 @@ def _lock_file(f: IO) -> None:
 
     def _lock_file(f: IO) -> None:
         # On Windows we lock a byte range and file must not be empty
-        f.write(b"\0")
+        f.write(" ")
         f.flush()
         f.seek(0)