How to listen to events from a browser window in Python

I'm making a plugin for Revit using python, which needs to interact with another web based tool called Speckle, which requires that the user login so we can get a JWT for interacting with the speckle API. When I've made other web based tools that connect to speckle, I've simply rendered the standard Speckle login pop-up in an iframe and listened for the event that sends back the JWT.

I thought I could do a similar thing by opening the Speckle login page using python's webbrowser module, but I'm not sure how to access the JWT once the user has logged in.

Any suggestions on how I could manage this?