No need to assign the results of expressions used only for side effects.
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index f63e719..2a4c156 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -920,7 +920,7 @@
             """Wait for child process to terminate.  Returns returncode
             attribute."""
             if self.returncode is None:
-                obj = WaitForSingleObject(self._handle, INFINITE)
+                WaitForSingleObject(self._handle, INFINITE)
                 self.returncode = GetExitCodeProcess(self._handle)
             return self.returncode