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/tests/test_readers.py

@@ -1,10 +1,7 @@
 # -*- coding: utf-8 -*-
-from __future__ import print_function, unicode_literals
 
 import os
 
-import six
-
 from pelican import readers
 from pelican.tests.support import get_settings, unittest
 from pelican.utils import SafeDatetime
@@ -64,8 +61,7 @@ class TestAssertDictHasSubset(ReaderTest):
         self.assertDictHasSubset(self.dictionary, self.dictionary)
 
     def test_fail_not_set(self):
-        six.assertRaisesRegex(
-            self,
+        self.assertRaisesRegex(
             AssertionError,
             r'Expected.*key-c.*to have value.*val-c.*but was not in Dict',
             self.assertDictHasSubset,
@@ -73,8 +69,7 @@ class TestAssertDictHasSubset(ReaderTest):
             {'key-c': 'val-c'})
 
     def test_fail_wrong_val(self):
-        six.assertRaisesRegex(
-            self,
+        self.assertRaisesRegex(
             AssertionError,
             r'Expected .*key-a.* to have value .*val-b.* but was .*val-a.*',
             self.assertDictHasSubset,
@@ -445,7 +440,7 @@ class RstReaderTest(ReaderTest):
     def test_parse_error(self):
         # Verify that it raises an Exception, not nothing and not SystemExit or
         # some such
-        with six.assertRaisesRegex(self, Exception, "underline too short"):
+        with self.assertRaisesRegex(Exception, "underline too short"):
             self.read_file(path='../parse_error/parse_error.rst')