rmdir can be easily done without calling the shell.

mpegize.py

@@ -418,8 +418,8 @@ class Mpegize:
         print("mpegize command base-dir destination-movie fps dng|grw")
 
     def cleanup(m):
-        os.system("rmdir %s/sm/" % m.base)
-        os.system("rmdir %s/" % m.base)
+        os.rmdir(m.base+"/sm/")
+        os.rmdir(m.base)
         print("Message: Rec")
         sys.stdout.flush()