php似乎没有运行exec命令

  $uploadedFile = $_FILES["files"]["name"];
  $uploadedFile = '"' . $uploadedFile . '"';
  echo $uploadedFile . "<br>";
  exec('/usr/bin/python /path/to/pyscript.py ' . $uploadedFile);

I have tried variations on this all to no effect. I have confirmed that the file, $uploadedFile, is being setup correctly. Also, the python script does have the correct permissions. There is noting in the php.ini to indicate that running the exec command is being blocked.

Any constructive help would be much appreciated.