Docs: drop Python 2 support

The kernel build system as a whole is dropping support for Python 2, so we
should do the same. The effects are rather small, especially considering
that much of the deleted code was not doing anything under any version of
Python anyway.

Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/sphinx/kfigure.py

···
 from os import path
 import subprocess
 from hashlib import sha1
-import sys
-
 from docutils import nodes
 from docutils.statemachine import ViewList
 from docutils.parsers.rst import directives
 from docutils.parsers.rst.directives import images
 import sphinx
-
 from sphinx.util.nodes import clean_astext
-from six import iteritems
-
 import kernellog
-
-PY3 = sys.version_info[0] == 3
-
-if PY3:
-    _unicode = str
-else:
-    _unicode = unicode
 
 # Get Sphinx version
 major, minor, patch = sphinx.version_info[:3]
···
     docname = app.env.docname
     labels = std.data["labels"]
 
-    for name, explicit in iteritems(doctree.nametypes):
+    for name, explicit in doctree.nametypes.items():
         if not explicit:
             continue
         labelid = doctree.nameids[name]

Documentation/sphinx/maintainers_include.py

···
         field_content = ""
 
         for line in open(path):
-            if sys.version_info.major == 2:
-                line = unicode(line, 'utf-8')
             # Have we reached the end of the preformatted Descriptions text?
             if descriptions and line.startswith('Maintainers'):
                 descriptions = False

Documentation/sphinx/requirements.txt

···
 docutils
 Sphinx==2.4.4
 sphinx_rtd_theme
-six

Documentation/sphinx/rstFlatTable.py

···
 # imports
 # ==============================================================================
 
-import sys
-
 from docutils import nodes
 from docutils.parsers.rst import directives, roles
 from docutils.parsers.rst.directives.tables import Table
···
 # ==============================================================================
 
 __version__  = '1.0'
-
-PY3 = sys.version_info[0] == 3
-PY2 = sys.version_info[0] == 2
-
-if PY3:
-    # pylint: disable=C0103, W0622
-    unicode     = str
-    basestring  = str
 
 # ==============================================================================
 def setup(app):

scripts/sphinx-pre-install

···
 					$need_virtualenv = 1;
 				}
 				if ($1 < 3) {
-					# Complain if it finds python2 (or worse)
-					printf "Warning: python$1 support is deprecated. Use it with caution!\n";
+					# Fail if it finds python2 (or worse)
+					die "Python 3 is required to build the kernel docs\n";
 				}
 			} else {
 				die "Warning: couldn't identify $python_cmd version!";