email: Catch exceptions during send.

Catch SMTPlib exceptions to avoid mercurial showing a backtrace during
an e.g. authentication error.

mercurial/mail.py

@@ -36,7 +36,10 b' def _smtp(ui):'
     if username and password:
         ui.note(_('(authenticating to mail server as %s)\n') %
                   (username))
-        s.login(username, password)
+        try:
+            s.login(username, password)
+        except smtplib.SMTPException, inst:
+            raise util.Abort(inst)
 
     def send(sender, recipients, msg):
         try: