«Class 'Df\Payment\Exception' not found»

I have this error log

[18-Jul-2017 09:53:20 UTC] PHP Fatal error: Class ‘Df\Payment\Exception’ not found in /home/sandbox/public_html/mage/vendor/mage2pro/core/Payment/W/Exception.php on line 9
[18-Jul-2017 09:53:20 UTC] PHP Fatal error: Class ‘Df\Payment\Exception’ not found in /home/sandbox/public_html/mage/vendor/mage2pro/core/Payment/W/Exception.php on line 9

is it because of my installation? or a bug?

thanks

My previous reply was wrong.
Thanks for reporting the important issue.
I have fixed it in the latest version (core 2.8.22, Stripe 1.9.24)