def ftp_PASS(self, password):
        """
        Second part of login.  Get the password the peer wants to
        authenticate with.
        """
        if self.factory.allowAnonymous and self._user == self.factory.userAnonymous:
            # anonymous login
            creds = credentials.Anonymous()
            reply = GUEST_LOGGED_IN_PROCEED
        else:
            # user login
            creds = credentials.UsernamePassword(self._user, password)
            reply = USR_LOGGED_IN_PROCEED
        del self._user

        def _cbLogin(result):
            (interface, avatar, logout) = result
            assert interface is IFTPShell, "The realm is busted, jerk."
            self.shell = avatar
            self.logout = logout
            self.workingDirectory = []
            self.state = self.AUTHED
            return reply

        def _ebLogin(failure):
            failure.trap(cred_error.UnauthorizedLogin, cred_error.UnhandledCredentials)
            self.state = self.UNAUTH
            raise AuthorizationError

        d = self.portal.login(creds, None, IFTPShell)
        d.addCallbacks(_cbLogin, _ebLogin)
        return d

        Second part of login.  Get the password the peer wants to
        authenticate with.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/ftp.py