A Python 3 application might only define `__next__`, not `next`.  Use
`six.next` instead.

This is very similar to https://github.com/cdent/paste/pull/53, and was
apparently missed there.

* Update next() to work with py3

* wsgi.errors is supposed to be text, fixes ErrorMiddleware on py3

The BaseCookie import is cleaned up to use six.

Where splittype and splithost are used the returned values are not, so they can go away.

* Patching auth ticket to be python3 compatible

In py2 an array is created and sorted, and in py3 an array of the items needs to be realized in the same fashion hence the sorted(•) fix. Otherwise the code will fail on Python 3 since dict.items() returns a view on the items which doesn't have a .sort() method.

If the app-iterator being passed in is not defining `next()` (e.g. running under py3 and only defined `__next__`), this will currently crash.

Fix by using `six.next` which will use `__next__` or `next` as appropriate.

* add ipv6 support by setting address family

* StringIO imports differently in python 3 - use six for compatibility

* Paste requires bytes like objects.  in python 2 cStringIO works fine, but in python three it needs to use io.BytesIO

* simplify imports and logic by using six.BytesIO exclusively for parsing body content