title: Running another python script with os.system
body: <p>I have old python. So can't use subprocess.
  I have two python scripts. One primary.py and another secondary.py.
  While running primary.py I need to run secondary.py.</p>
  
  <p>Format to run secondary.py is 'python secondary.py Argument'</p>
  
  <p><code>os.system('python secondary.py Argument')...is giving error saying that can't open file 'Argument': [Errno 2] No such file or directory</code></p>