warning: invalid credential line: [0x7FFEF7EABC10] ANOMALY: meaningless REX prefix used?

I'm following this guide: https://docs.microsoft.com/en-us/azure/app-service-web/app-service-web-nodejs-sails-cli-nodejs

I'm getting this error when i try to

 git push azure master

Error: warning: invalid credential line: [0x7FFEF7EABC10] ANOMALY: meaningless REX prefix used?

What is exactly happening?

Thanks,

via Logan_B