#14925: email now registers a defect for missing header/body separator.

This patch also deprecates the MalformedHeaderDefect.  My best guess is that
this defect was rendered obsolete by a refactoring of the parser, and the
corresponding defect for the new parser (which this patch introduces) was
overlooked.
diff --git a/Lib/email/errors.py b/Lib/email/errors.py
index f916229..aa836d4 100644
--- a/Lib/email/errors.py
+++ b/Lib/email/errors.py
@@ -48,8 +48,10 @@
 class MisplacedEnvelopeHeaderDefect(MessageDefect):
     """A 'Unix-from' header was found in the middle of a header block."""
 
-class MalformedHeaderDefect(MessageDefect):
-    """Found a header that was missing a colon, or was otherwise malformed."""
+class MissingHeaderBodySeparatorDefect(MessageDefect):
+    """Found line with no leading whitespace and no colon before blank line."""
+# XXX: backward compatibility, just in case (it was never emitted).
+MalformedHeaderDefect = MissingHeaderBodySeparatorDefect
 
 class MultipartInvariantViolationDefect(MessageDefect):
     """A message claimed to be a multipart but no subparts were found."""