fa45123f66 test: Add .style.yapf (MarcoFalke)
Pull request description:
This can *optionally* be used to format any added code before submitting a pull. I use this heavily and wouldn't want to hold it back from others, now that yapf is referred to in https://github.com/bitcoin/bitcoin/blob/master/doc/productivity.md#format-python-diffs-with-yapf-diffpy
Tree-SHA512: 0f3d8bcbb76a710d9faa1226202073e8d967a82a05fc002cd10305ff58b382f5ff3df96a6faaec5bd01613d41f5fc2343e4999fb1217bf1f24f6da186d572ca1
