* Replaced all from ...py23 import * with explicit name imports, or removed completely when possible.
* Replaced tounicode() with tostr()
* Changed all BytesIO ans StringIO imports to from io import ..., replaced all UnicodeIO with StringIO.
* Replaced all unichr() with chr()
* Misc minor tweaks and fixes
It seems like sets are hashed differently in CPython and PyPy.
Because of this, the returned list of class sets may have a different sort
order (within each class size) between the two implementations.
For now, I make the test pass on both CPython and PyPy by casting the returned
list of sets into a set of (frozen) sets, and asserting that its *content* is
correct, without considering the *order* of the sets in the list.
set objects have different __repr__ on python 2 and 3
Python 3:
>>> {1, 2, 3}
{1, 2, 3}
Python 2
>>> {1, 2, 3}
set([1, 2, 3])
(one among the several reasons I don't particularly like doctest...)
