(Python) Wrong highlighting of default arguments

[wjandrea]

Describe the issue
None should be the same colour in the function signature and function body (since it's the same object being referred to), but instead it's plain in in the signature and colored in the body.

Screenshots from this Stack Overflow post (dark and light mode):

Which language seems to have the issue?
python/py

Are you using highlight or highlightAuto?
I don't know what that means. I assume it's about how highlight.js is deployed, but I'm an end user, not a Stack Exchange dev.

Sample Code to Reproduce

def my_func(working_list=None):
    if working_list is None: 
        working_list = []

    working_list.append("a")
    print(working_list)

Expected behavior
None should be the same colour in the function signature and function body. GitHub gets it right (see snippet above). And FWIW, here are screenshots from Atom, PythonAnywhere, and gedit, which are all using different highlighting schemes to GitHub:

Additional context
I originally posted this bug report on Stack Overflow and was directed here by Martijn Pieters.

[joshgoebel]

Confirm (at a glance). We don't now match keywords inside params... a simple fix for this would involve figuring out which keywords can existing inside params and then adding a keywords option to the inner matcher of PARAMS.

Care to try for a PR? :-)