README: Example assumes Python 2

[Chealer]

The README file’s example calls the print statement, which is replaced by the print function in Python 3, meaning it now fails:

print ppretty(…)
^^^^^^^^^^^^^^^

SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

License

This report (including all messages and attachments I add to it) is offered under the terms of CC0 1.0.

[symonsoft]

Yes. Example was written in the times of Python 2. But It also tested with Python 3