[docs] Bug in part 5 of the Python 3 tutorial

[Eli Bendersky]

> In the Python 3 tutorial about data structures, in the section about nested
> list comprehensions
> (http://docs.python.org/py3k/tutorial/datastructures.html#nested-list-comprehensions);
> the zip function is described differently than it works in my installation
> (Ubuntu 12.04). I'm fairly new to Python so the issue is probably described
> best using an example:
>
>     $ python3
>     Python 3.2.3 (default, May  3 2012, 15:51:42)
>     [GCC 4.6.3] on linux2
>     Type "help", "copyright", "credits" or "license" for more information.
>     >>> matrix = [
>     ...     [1, 2, 3, 4],
>     ...     [5, 6, 7, 8],
>     ...     [9, 10, 11, 12],
>     ... ]
>     >>> zip(*matrix)
>     <zip object at 0x1053098>
>
> However, in the tutorial the zip function returns a list of tuplets like
> this:
>
>     >>> zip(*matrix)
>     [(1, 5, 9), (2, 6, 10), (3, 7, 11), (4, 8, 12)]
>
> In order to get that result, I have to do this in my installation:
>
>     >>> list(zip(*matrix))
>     [(1, 5, 9), (2, 6, 10), (3, 7, 11), (4, 8, 12)]
>

Without looking too deep into it, it appears that the example has not
been ported to Python 3. Please open an issue in the bug tracker for
this.

Eli