Refs #23919 -- Removed six.PY2/PY3 usage

Thanks Tim Graham for the review.

django/utils/_os.py

@@ -1,41 +1,18 @@
 import os
-import sys
 import tempfile
-from os.path import abspath, dirname, isabs, join, normcase, normpath, sep
+from os.path import abspath, dirname, join, normcase, sep
 
 from django.core.exceptions import SuspiciousFileOperation
-from django.utils import six
 from django.utils.encoding import force_text
 
-if six.PY2:
-    fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()
 
-
-# Under Python 2, define our own abspath function that can handle joining
-# unicode paths to a current working directory that has non-ASCII characters
-# in it.  This isn't necessary on Windows since the Windows version of abspath
-# handles this correctly. It also handles drive letters differently than the
-# pure Python implementation, so it's best not to replace it.
-if six.PY3 or os.name == 'nt':
-    abspathu = abspath
-else:
-    def abspathu(path):
-        """
-        Version of os.path.abspath that uses the unicode representation
-        of the current working directory, thus avoiding a UnicodeDecodeError
-        in join when the cwd has non-ASCII characters.
-        """
-        if not isabs(path):
-            path = join(os.getcwdu(), path)
-        return normpath(path)
+abspathu = abspath
 
 
 def upath(path):
     """
     Always return a unicode path.
     """
-    if six.PY2 and not isinstance(path, six.text_type):
-        return path.decode(fs_encoding)
     return path
 
 
@@ -44,8 +21,6 @@ def npath(path):
     Always return a native path, that is unicode on Python 3 and bytestring on
     Python 2.
     """
-    if six.PY2 and not isinstance(path, bytes):
-        return path.encode(fs_encoding)
     return path