Remove six usage

sphinx-feature-classification was declared python-3-only by change
I0f3e9d980c25545a in release 1.0.1 (2020-04-07 10:02:33 +0000).
It's never had six in requirements.txt despite importing six in
two files.  Now that consuming projects are all python-3-only,
six is not being pulled in by some other project's requirements.
So convert six usage to pure python 3.

Change-Id: I1917fda331860332242774019ac7ca54512430e3

sphinx_feature_classification/support_matrix.py

@@ -18,14 +18,12 @@ It is used via a single directive in the .rst file
   .. support_matrix::
 
 """
-
+import configparser
 from os import path
 import re
 
 from docutils import nodes
 from docutils.parsers import rst
-import six
-from six.moves import configparser
 from sphinx.util.fileutil import copy_asset
 
 KEY_PATTERN = re.compile("[^a-zA-Z0-9_]")
@@ -222,11 +220,6 @@ class Directive(rst.Directive):
         fname = self.arguments[0]
         rel_fpath, fpath = env.relfn2path(fname)
 
-        # Handle deprecation of readfp in py3 for read_file that was not
-        # available in py2.
-        if six.PY2:
-            cfg.read_file = cfg.readfp
-
         with open(fpath) as fp:
             cfg.read_file(fp)
 

sphinx_feature_classification/tests/test_sphinx_feature_classification.py

@@ -18,12 +18,11 @@ test_sphinx_feature_classification
 
 Tests for `sphinx_feature_classification` module.
 """
+import configparser
 import os
 
 import ddt
 import fixtures
-import six
-from six.moves import configparser
 
 from sphinx_feature_classification import support_matrix
 from sphinx_feature_classification.tests import base
@@ -39,9 +38,6 @@ class MatrixTestCase(base.TestCase):
         directory = os.path.dirname(os.path.abspath(__file__))
         config_file = os.path.join(directory, 'fakes', 'support-matrix.ini')
 
-        if six.PY2:
-            cfg.read_file = cfg.readfp
-
         with open(config_file) as fp:
             cfg.read_file(fp)