How to create a pop up window to authenticate bitbucket account?

I'm developing a website using Flask. I created an "update" button which would run "git pull" after click. The views.py file looks like this:

    @view_bp.route('/pull', methods = ['POST'])
    @login_required
    def pull():
        output = subprocess.check_output(["git", "pull"])
        return "done"

But after click, it would ask for bitbucket account in terminal and I have to authenticate my account in terminal:

    Username for 'https://bitbucket.org':
    Password for 'https://xxxxxxx@bitbucket.org':

What I want is a pop up window to log in bitbucket account and do the "git pull" thing after authentication. So how can I do it?

Thanks in advance!