Heroku, No default language could be detected for this app, what should I do?

Question

Python

! No default language could be detected for this app. HINT: This occurs when Heroku cannot detect the buildpack to use for this application automatically. See https://devcenter.heroku.com/articles/buildpacks ! Push failed

All files are on GitHub, but heroku is not defined, as I understand it, the language of the code, why?

Link to GitHub: https://github.com/advokappa/testbot