Document doctest's generator-future hack.
diff --git a/Lib/doctest.py b/Lib/doctest.py
index fc826df..3062f63 100644
--- a/Lib/doctest.py
+++ b/Lib/doctest.py
@@ -348,6 +348,13 @@
# 0,9,7 9-Feb-2001
# string method conversion
+# XXX Until generators are part of the language, examples in doctest'ed
+# modules will inherit doctest's __future__ settings (see PEP 236 for
+# more on that). In the absence of a better working idea, the std
+# test suite needs generators, while the set of doctest'ed modules that
+# don't use "yield" in a generator context may well be empty. So
+# enable generators here. This can go away when generators are no
+# longer optional.
from __future__ import generators
__version__ = 0, 9, 7