Best practice design or modules for displaying errors to user [on hold]

On this open source project (Github link) we have users upload a file which is then parsed by python to create a javascript application (php holds it together).

The user input may have errors or features that should generate warnings. If this was just a stand alone python script I'd use these guidelines to produce user output, but I'm looking for the 'pattern' that lets me neatly pass information from the python back to the user. I can imagine:

• Have the python generate, effectively, a webpage that will be shown to the user
• Have the python output warnings and errors to stdout and use some magic php script to show them nicely to the user.
• Some other thing.

What's the best practice here?