noted sub_channel being renamed to iopub_channel

docs/source/whatsnew/development.txt

@@ -1,40 +1,42 b''
 =====================
  Development version
 =====================
 
 This document describes in-flight development work.
 
 The CodeMirror js library has been updated fron 2.23 to 2.32 
 this might induce a few changes in behavior of keymaps in the notebook, 
 especially intenting/deindenting blocks that is now bound to Ctrl+] and ctr+[
 
 * Exception types can now be displayed with a custom traceback, by defining a
   ``_render_traceback_()`` method which returns a list of strings, each
   containing one line of the traceback.
 * A new command, ``ipython history trim`` can be used to delete everything but
   the last 1000 entries in the history database.
 
 In-process kernels
 ------------------
 
 The Python-language frontends, particularly the Qt console, may now communicate
 with in-process kernels, in addition to the traditional out-of-process
 kernels. An in-process kernel permits direct access to the kernel namespace,
 which is necessary in some applications. It should be understood, however, that
 the in-process kernel is not robust to bad user input and will block the main
 (GUI) thread while executing. Developers must decide on a case-by-case basis
 whether this tradeoff is appropriate for their application.
 
 Backwards incompatible changes
 ------------------------------
 
 * Calling :meth:`InteractiveShell.prefilter` will no longer perform static
   transformations - the processing of escaped commands such as ``%magic`` and
   ``!system``, and stripping input prompts from code blocks. This functionality
   was duplicated in :mod:`IPython.core.inputsplitter`, and the latter version
   was already what IPython relied on. A new API to transform input will be ready
   before release.
 * Functions from :mod:`IPython.lib.inputhook` to control integration with GUI
   event loops are no longer exposed in the top level of :mod:`IPython.lib`.
   Code calling these should make sure to import them from
   :mod:`IPython.lib.inputhook`.
+* For all kernel managers, the ``sub_channel`` attribute has been renamed to
+  ``iopub_channel``.