RFE: lease drop use six module

[kloczek]

Looks like bleach still is using six

[tkloczko@pers-jacek bleach-6.0.0]$ grep -rw six
CHANGES:* Add ``six>=1.9`` to requirements. Thank you, Dave Shawley (#416)
CHANGES:* Update all code to be compatible with Python 3 and 2 using six.
bleach/_vendor/html5lib-1.1.dist-info/METADATA:Requires-Dist: six (>=1.9)
bleach/_vendor/html5lib-1.1.dist-info/METADATA:* Add explicit dependency for six >= 1.9. (Thank you, Eric Amorde!)
bleach/_vendor/html5lib-1.1.dist-info/METADATA:* Python 3.2+ supported in a single codebase using the ``six`` library.
bleach/_vendor/html5lib/_inputstream.py:from six import text_type
bleach/_vendor/html5lib/_inputstream.py:from six.moves import http_client, urllib
bleach/_vendor/html5lib/_tokenizer.py:from six import unichr as chr
bleach/_vendor/html5lib/_trie/py.py:from six import text_type
bleach/_vendor/html5lib/_utils.py:from six import text_type, PY3
bleach/_vendor/html5lib/filters/lint.py:from six import text_type
bleach/_vendor/html5lib/filters/sanitizer.py:from six.moves import urllib_parse as urlparse
bleach/_vendor/html5lib/html5parser.py:from six import with_metaclass, viewkeys
bleach/_vendor/html5lib/serializer.py:from six import text_type
bleach/_vendor/html5lib/treebuilders/base.py:from six import text_type
bleach/_vendor/html5lib/treebuilders/etree.py:from six import text_type
bleach/_vendor/html5lib/treebuilders/etree_lxml.py:from six import PY3, binary_type
bleach/_vendor/html5lib/treewalkers/etree.py:from six import string_types
bleach/_vendor/html5lib/treewalkers/etree_lxml.py:from six import text_type
setup.py:    "six>=1.9.0",

Good example about how to that:
ckan/ckan#6267

[kloczek]

Just found that ticket againt that is alredy created #618
Closing as duplicated.