title: python subprocess "mount" does not prompt for password
body: <p>I just learned subprocess.check_call() function today. I intend to use it to replace my os.system command.</p>
  
  <p>Originally, I have my command as such:</p>
  
  <pre><code>os.system("mount -t cifs //source/share /mnt/share -o username=user")
  </code></pre>
  
  <p>The command above will prompt for password and it will mount the drive if the password is correct.</p>
  
  <p>However, if I tried:</p>
  
  <pre><code>cmd_string="mount -t cifs //source/share /mnt/share -o username=user"
  
  subprocess.check_call(cmd_string.split(" "), shell=True, stdin=sys.stdin)
  </code></pre>
  
  <p>It would not ask for password. Instead, it just print the partitions. It's like invoke "mount" command without parameters. </p>
  
  <p>Any idea how I can use check_call and still receive interactive input from user?</p>