Remove dependency on six (#8650)

Fixes https://github.com/certbot/certbot/issues/8494.

I left the `six` dependency pinned in `tests/letstest/requirements.txt` and `tools/oldest_constraints.txt` because `six` is still a transitive dependency with our current pinnings.

The extra moving around of imports is due to me using `isort` to help me keep dependencies in sorted order after replacing imports of `six`.

* remove some six usage in acme

* remove six from acme

* remove six.add_metaclass usage

* fix six.moves.zip

* fix six.moves.builtins.open

* six.moves server fixes

* 's/six\.moves\.range/range/g'

* stop using six.moves.xrange

* fix urllib imports

* s/six\.binary_type/bytes/g

* s/six\.string_types/str/g

* 's/six\.text_type/str/g'

* fix six.iteritems usage

* fix itervalues usage

* switch from six.StringIO to io.StringIO

* remove six imports

* misc fixes

* stop using six.reload_module

* no six.PY2

* rip out six

* keep six pinned in oldest constraints

* fix log_test.py

* update changelog

4 files changed, 7 insertions, 16 deletions

diff --git a/certbot-apache/certbot_apache/_internal/interfaces.py b/certbot-apache/certbot_apache/_internal/interfaces.py
index 647790c41..77daa5b56 100644
--- a/certbot-apache/certbot_apache/_internal/interfaces.py
+++ b/certbot-apache/certbot_apache/_internal/interfaces.py
@@ -100,12 +100,10 @@ For this reason the internal representation of data should not ignore the case.
 """
 
 import abc
-import six
 
 
 
-@six.add_metaclass(abc.ABCMeta)
-class ParserNode(object):
+class ParserNode(object, metaclass=abc.ABCMeta):
     """
     ParserNode is the basic building block of the tree of such nodes,
     representing the structure of the configuration. It is largely meant to keep
@@ -204,9 +202,7 @@ class ParserNode(object):
         """
 
 
-# Linter rule exclusion done because of https://github.com/PyCQA/pylint/issues/179
-@six.add_metaclass(abc.ABCMeta)  # pylint: disable=abstract-method
-class CommentNode(ParserNode):
+class CommentNode(ParserNode, metaclass=abc.ABCMeta):
     """
     CommentNode class is used for representation of comments within the parsed
     configuration structure. Because of the nature of comments, it is not able
@@ -249,8 +245,7 @@ class CommentNode(ParserNode):
                                           metadata=kwargs.get('metadata', {}))  # pragma: no cover
 
 
-@six.add_metaclass(abc.ABCMeta)
-class DirectiveNode(ParserNode):
+class DirectiveNode(ParserNode, metaclass=abc.ABCMeta):
     """
     DirectiveNode class represents a configuration directive within the configuration.
     It can have zero or more parameters attached to it. Because of the nature of
@@ -325,8 +320,7 @@ class DirectiveNode(ParserNode):
         """
 
 
-@six.add_metaclass(abc.ABCMeta)
-class BlockNode(DirectiveNode):
+class BlockNode(DirectiveNode, metaclass=abc.ABCMeta):
     """
     BlockNode class represents a block of nested configuration directives, comments
     and other blocks as its children. A BlockNode can have zero or more parameters
diff --git a/certbot-apache/certbot_apache/_internal/parser.py b/certbot-apache/certbot_apache/_internal/parser.py
index 4d997545b..75be0833f 100644
--- a/certbot-apache/certbot_apache/_internal/parser.py
+++ b/certbot-apache/certbot_apache/_internal/parser.py
@@ -5,7 +5,6 @@ import logging
 import re
 import sys
 
-import six
 
 from acme.magic_typing import Dict
 from acme.magic_typing import List
@@ -275,7 +274,7 @@ class ApacheParser(object):
         while len(mods) != prev_size:
             prev_size = len(mods)
 
-            for match_name, match_filename in six.moves.zip(
+            for match_name, match_filename in zip(
                     iterator, iterator):
                 mod_name = self.get_arg(match_name)
                 mod_filename = self.get_arg(match_filename)
diff --git a/certbot-apache/tests/autohsts_test.py b/certbot-apache/tests/autohsts_test.py
index d15600215..db1c46b52 100644
--- a/certbot-apache/tests/autohsts_test.py
+++ b/certbot-apache/tests/autohsts_test.py
@@ -7,7 +7,6 @@ try:
     import mock
 except ImportError: # pragma: no cover
     from unittest import mock # type: ignore
-import six  # pylint: disable=unused-import  # six is used in mock.patch()
 
 from certbot import errors
 from certbot_apache._internal import constants
diff --git a/certbot-apache/tests/configurator_test.py b/certbot-apache/tests/configurator_test.py
index 6753995c6..302bf0023 100644
--- a/certbot-apache/tests/configurator_test.py
+++ b/certbot-apache/tests/configurator_test.py
@@ -10,7 +10,6 @@ try:
     import mock
 except ImportError: # pragma: no cover
     from unittest import mock # type: ignore
-import six  # pylint: disable=unused-import  # six is used in mock.patch()
 
 from acme import challenges
 from certbot import achallenges
@@ -726,7 +725,7 @@ class MultipleVhostsTest(util.ApacheTest):
         # This calls open
         self.config.reverter.register_file_creation = mock.Mock()
         mock_open.side_effect = IOError
-        with mock.patch("six.moves.builtins.open", mock_open):
+        with mock.patch("builtins.open", mock_open):
             self.assertRaises(
                 errors.PluginError,
                 self.config.make_vhost_ssl, self.vh_truth[0])
@@ -1834,7 +1833,7 @@ class InstallSslOptionsConfTest(util.ApacheTest):
 
     def test_open_module_file(self):
         mock_open = mock.mock_open(read_data="testing 12 3")
-        with mock.patch("six.moves.builtins.open", mock_open):
+        with mock.patch("builtins.open", mock_open):
             self.assertEqual(self.config._open_module_file("/nonsense/"), "testing 12 3")
 
 if __name__ == "__main__":