Dont use print. This will work only with python 2. in Python 3, this changes to the print() function. Better would be to use the print functionality in click. It takes care of a lot of cross platform issues while building CLI tools. https://github.com/logicbomb-1/github-secret-scan/blob/master/gss.py#L241
Also, it is important to treat the stdin stream for what it is meant for. The stdin stream must be used to print only things that are not errors because it makes it hard to pipe the response to another command for further processing. The right way to print this to the console would be to print it to stderr. Use click to do this.
Firstly, prefer using click. It is cross platform and is generally a much better library to use than argparse.
Also, add support for the following options:
--help for the CLI. Click has support for this.
--username - so that a user can be scanned
--repo - what about scanning only one repo? It is possible that someone wants to scan only one or more of their repos. It should be possible to do that.