title: PrettyPrint python into a string, and not stdout
body: <p>I'd like to use prettyprint to print out a dictionary, but into a string and not to console.
  This string is to be passed on to other functions.</p>
  
  <p>I know I can use the "stream" parameter to specify a file instead of sys.out but I want a string.</p>
  
  <p>How do I do that?</p>