Alter md5 call to make utils.py module FIPS compatible

[relativistic]

The utils.py module uses hashlib.md5. This fails on a FIPS system, where using the md5 function raises a ValueError.

It does not appear that the md5 function is used for security purposes in utils.py. I think the fix would be simply set usedforsecurity=False to allow the md5 function to work on a FIPS system.

So the new function would be:

@toolz.memoize
def color_of(x, palette=palette):
    h = md5(str(x).encode(), usedforsecurity=False)
    n = int(h.hexdigest()[:8], 16)
    return palette[n % len(palette)]

[jacobtomlinson]

That seems reasonable to me. Do you have any interest in making a PR to make this change @relativistic?

[relativistic]

I've not submitted a PR to github before, but I can give it a try @jacobtomlinson.

I'm not clear from looking at the contributions page how to best test this before submitting the PR. Should I just make the change, submit the PR, and then let the github-actions system run unit tests for me?

[jacobtomlinson]

It's a tricky one to test because we have no way of testing on a FIPS system. We could mock things out, but that seems like overkill. I would just suggest making a PR and letting the CI run the tests and provided nothing majorly breaks I would be fine merging this in.

[relativistic]

Yeah, I ran the local tests, and not everything passed, but that was even before I made any changes. So I'm not sure which tests to verify!

I'll try doing the PR.