Make sure to log a proper exception when an email error occurs

util/useremails.py

@@ -41,6 +41,7 @@ def send_email(recipient, subject, template_file, parameters):
   try:
     mail.send(msg)
   except Exception as ex:
+    logger.exception('Error while trying to send email to %s', recipient)
     raise CannotSendEmailException(ex.message)
 
 def send_password_changed(username, email):