Fix 2.7ism.
diff --git a/Doc/library/constants.rst b/Doc/library/constants.rst
index 80e792c..e6d927a 100644
--- a/Doc/library/constants.rst
+++ b/Doc/library/constants.rst
@@ -42,17 +42,14 @@
.. data:: __debug__
This constant is true if Python was not started with an :option:`-O` option.
- See also the :keyword:`assert` statement.
+ It cannot be reassigned. See also the :keyword:`assert` statement.
.. note::
- The names :data:`None` and :data:`__debug__` cannot be reassigned
- (assignments to them, even as an attribute name, raise :exc:`SyntaxError`),
- so they can be considered "true" constants.
-
- .. versionchanged:: 2.7
- Assignments to ``__debug__`` as an attribute became illegal.
+ The name :data:`None` cannot be reassigned (assignments to it, even as an
+ attribute name, raise :exc:`SyntaxError`), so it can be considered a "true"
+ constant.
Constants added by the :mod:`site` module