six: use py3compat as six wrapper, term done

The old porting approach to six became quite messy. Instead let's try
to work through a diff of py2 with py3 after 2to3 and deactivate 2to3
one by one whenever a file is done. In the process the tests are meant
to always pass.
dropping support for python 3.2 as it doesn't allow u"" strings
six: compatibility for non byte string docstrings

files without `from __futur__ import unicode_literals` header might
push utf-8 encoded byte strings with non ascii chars through
format_doctest_out causing encoding errors when trying to replace u"",
b"", ... prefixes which are now unicode literals because of that header.