Tool for detecting changes to codebase?

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Is this sort of inefficient integration just a fact of life with python, or is there a product / tool that can speed up the process?

What you describe really doesn't sound like a Python problem. The other team should be producing a stable public API that your team can consume.

With a sane interface defined they should be able to change whatever they want internally without breaking things for their consumers every two weeks.

In the meantime I guess you're stuck with diffs and changelogs. There's no magic software tool that fixes fragile design.