Nice. I also looked into this a while ago and came up with a very simplistic (few lines) Python implementation that does this and even allows for some customization: https://gist.github.com/fladd/36c422f1c0e9bf02f41f9fad19609d...
But my goal was not really the progress bars, but the placing of it below the logs.
And then I didn't wonder. Good work.