No need to assign the results of expressions used only for side effects.
diff --git a/Lib/rexec.py b/Lib/rexec.py
index 22b1bb2..7446151 100644
--- a/Lib/rexec.py
+++ b/Lib/rexec.py
@@ -244,7 +244,7 @@
         m.open = m.file = self.r_open
 
     def make_main(self):
-        m = self.add_module('__main__')
+        self.add_module('__main__')
 
     def make_osname(self):
         osname = os.name