[docs] Trivial argparse documentation bug.

[Tom Sillence]

Hi,

Re: the documentation for the standard library argparse module, there would seem to be a trivial mistake under "15.4.5.9. Exiting methods":

http://docs.python.org/library/argparse.html#exiting-methods

The ArgumentParser.error method is described as printing "a usage message ... to the standard output". In fact, though, the source suggests it is printed to standard error, not standard output.

Cheers!

Tom S.