def test_requireTransportSecurityTLSOfferedOverSSL(self):
        """
        When C{requireTransportSecurity} is C{True} and the client is connected
        over an SSL transport, if the server offers the I{STARTTLS}
        extension, it is not used before mail is delivered.
        """
        self._requireTransportSecurityOverSSLTest(
            b"250-AUTH LOGIN\r\n"
            b"250 STARTTLS\r\n")

        When C{requireTransportSecurity} is C{True} and the client is connected
        over an SSL transport, if the server offers the I{STARTTLS}
        extension, it is not used before mail is delivered.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_smtp.py