Have MimeWriter raise a DeprecationWarning as per PEP 4 and its documentation.
diff --git a/Lib/MimeWriter.py b/Lib/MimeWriter.py
index 58c0a0b..e898f9f 100644
--- a/Lib/MimeWriter.py
+++ b/Lib/MimeWriter.py
@@ -14,6 +14,11 @@
 
 __all__ = ["MimeWriter"]
 
+import warnings
+
+warnings.warn("the MimeWriter module is deprecated; use the email package instead",
+                DeprecationWarning, 2)
+
 class MimeWriter:
 
     """Generic MIME writer.