tools (common/email): fixed email sending after python 3 port

sat/tools/common/email.py

@@ -62,7 +62,7 @@ def sendEmail(config, to_emails, subject="", body="", from_email=None):
         email_host.encode("utf-8"),
         email_from.encode("utf-8"),
         [email.encode("utf-8") for email in to_emails],
-        msg.as_string(),
+        msg.as_bytes(),
         senderDomainName=email_sender_domain.encode("utf-8") if email_sender_domain
                                                              else None,
         port=email_port,