Raincoat has you covered when you can’t stay DRY.
See the [FR] slides of the lightning talk I gave at PyConFr 2016 in Rennes (which happens to be prononced more or less like “rain”, but that’s a fluke).
Raincoat is a tool that is aimed toward helping you tracking your copy/paste dependencies. In other words, it warns you when code you have copy/pasted is updated upstream, so that you can backport bugfixes and security fixes.
Enjoy! And as usual, feel free to ping me on Twitter!