#12515: email now registers a defect if the MIME end boundary is missing.

This commit also restores the news item for 167256 that it looks like
Terry inadvertently deleted.  (Either that, or I don't understand
now merging works...which is equally possible.)
diff --git a/Doc/library/email.errors.rst b/Doc/library/email.errors.rst
index 2bc3164..acfa6b2 100644
--- a/Doc/library/email.errors.rst
+++ b/Doc/library/email.errors.rst
@@ -73,6 +73,11 @@
 * :class:`StartBoundaryNotFoundDefect` -- The start boundary claimed in the
   :mailheader:`Content-Type` header was never found.
 
+* :class:`CloseBoundaryNotFoundDefect` -- A start boundary was found, but
+  no corresponding close boundary was ever found.
+
+  .. versionadded: 3.3
+
 * :class:`FirstHeaderLineIsContinuationDefect` -- The message had a continuation
   line as its first header line.