Document PyErr_WarnEx.  (Bad Neal!  No biscuit!)
Document PyErr_WarnEx.  (Bad Neal!  No biscuit!)

Is the explanation of the 'stacklevel' parameter clear?  Please feel free
to edit it.

I don't have LaTeX installed on this machine, so haven't verified that the
markup is correct.  Will check tonight, or maybe the automatic doc build will
tell me.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator