#4617: Previously it was illegal to delete a name from the local

namespace if it occurs as a free variable in a nested block.  This limitation
of the compiler has been lifted, and a new opcode introduced (DELETE_DEREF).

This sample was valid in 2.6, but fails to compile in 3.x without this change::

   >>> def f():
   ...     def print_error():
   ...        print(e)
   ...     try:
   ...        something
   ...     except Exception as e:
   ...        print_error()
   ...        # implicit "del e" here


This sample has always been invalid in Python, and now works::

   >>> def outer(x):
   ...     def inner():
   ...        return x
   ...     inner()
   ...     del x

There is no need to bump the PYC magic number: the new opcode is used
for code that did not compile before.

Doc/reference/simple_stmts.rst

@@ -388,11 +388,6 @@ namespace, depending on whether the name occurs in a :keyword:`global` statement
 in the same code block.  If the name is unbound, a :exc:`NameError` exception
 will be raised.
 
-.. index:: pair: free; variable
-
-It is illegal to delete a name from the local namespace if it occurs as a free
-variable in a nested block.
-
 .. index:: pair: attribute; deletion
 
 Deletion of attribute references, subscriptions and slicings is passed to the
@@ -400,6 +395,10 @@ primary object involved; deletion of a slicing is in general equivalent to
 assignment of an empty slice of the right type (but even this is determined by
 the sliced object).
 
+.. versionchanged:: 3.2
+   Previously it was illegal to delete a name from the local namespace if it
+   occurs as a free variable in a nested block.
+
 
 .. _return: