Initial pass of removing Python 2 support

This commit removes Six as a dependency for Pelican, replacing the
relevant aliases with the proper Python 3 imports. It also removes
references to Python 2 logic that did not require Six.

pelican/rstdirectives.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-from __future__ import print_function, unicode_literals
 
 import re
 
@@ -10,8 +9,6 @@ from pygments import highlight
 from pygments.formatters import HtmlFormatter
 from pygments.lexers import TextLexer, get_lexer_by_name
 
-import six
-
 import pelican.settings as pys
 
 
@@ -49,7 +46,7 @@ class Pygments(Directive):
 
         # Fetch the defaults
         if pys.PYGMENTS_RST_OPTIONS is not None:
-            for k, v in six.iteritems(pys.PYGMENTS_RST_OPTIONS):
+            for k, v in pys.PYGMENTS_RST_OPTIONS.items():
                 # Locally set options overrides the defaults
                 if k not in self.options:
                     self.options[k] = v