Merged revisions 67171 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r67171 | benjamin.peterson | 2008-11-08 12:38:54 -0600 (Sat, 08 Nov 2008) | 4 lines

  check for assignment to __debug__ during AST generation

  Also, give assignment to None a better error message
........

Python/ast.c

@@ -354,6 +354,7 @@ static const char* FORBIDDEN[] = {
     "None",
     "True",
     "False",
+    "__debug__",
     NULL,
 };