title: python isfile is not working here
body: <p>This is something I can't figure out why not working.
  I have purposely set sd_path so that it does not exist, and I am expecting it to go to the "does not exist" exception, and exit the code. But, rather, it is not raising any error, and going to "All Fine"</p>
  
  <pre><code>sd_path = "/home/rudra/foo/src/bar"
  try:
    os.path.isfile(sd_path)
    try:
      os.access(sd_path, os.X_OK)
    except:
      print("Executable "+sd_path+" does not have suitable permission")
      sys.exit(3)
  except:
    print("Executable "+sd_path+" does not exists")
    sys.exit(3)
  print("All Fine")
  </code></pre>