'git push heroku master' is still asking for authentication

Even if I executed heroku longin and entered username and password, I keep getting failed login error.

When asked for git heroku credentials enter the following:

username: <leave empty>
password: heroku auth token

Note: the heroku auth token can be retrieved using the following command:
heroku auth:token

Source: https://stackoverflow.com/questions/27810419/git-push-heroku-master-is-still-asking-for-authentication