Remove a Python 3.2 hack

Originally added in 3d3a75c

Author: jleclanche

oauth2_provider/oauth2_validators.py

@@ -1,6 +1,5 @@
 from __future__ import unicode_literals
 
-import six
 import base64
 import binascii
 import logging
@@ -64,11 +63,6 @@ def _authenticate_basic_auth(self, request):
         except AttributeError:
             encoding = 'utf-8'
 
-        # Encode auth_string to bytes. This is needed for python3.2 compatibility
-        # because b64decode function only supports bytes type in input.
-        if isinstance(auth_string, six.string_types):
-            auth_string = auth_string.encode(encoding)
-
         try:
             b64_decoded = base64.b64decode(auth_string)
         except (TypeError, binascii.Error):