Replaced "not PY3" by "PY2", new in six 1.4.0.

django/utils/_os.py

@@ -12,7 +12,7 @@ except NameError:
     class WindowsError(Exception):
         pass
 
-if not six.PY3:
+if six.PY2:
     fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()
 
 
@@ -38,7 +38,7 @@ def upath(path):
     """
     Always return a unicode path.
     """
-    if not six.PY3 and not isinstance(path, six.text_type):
+    if six.PY2 and not isinstance(path, six.text_type):
         return path.decode(fs_encoding)
     return path
 
@@ -47,7 +47,7 @@ def npath(path):
     Always return a native path, that is unicode on Python 3 and bytestring on
     Python 2.
     """
-    if not six.PY3 and not isinstance(path, bytes):
+    if six.PY2 and not isinstance(path, bytes):
         return path.encode(fs_encoding)
     return path