:meth:`!SMTP.auth_cram_md5` now raises an :exc:`~smtplib.SMTPException`
instead of a :exc:`ValueError` if Python has been built without MD5 support.
In particular, :class:`~smtplib.SMTP` clients will not attempt to use this
method even if the remote server is assumed to support it. Patch by Bénédikt
Tran.
