Pro tip: When you rely on Fabric to provision your servers, and your fabfile installs packages from the Cheeseshop, and package D (which you specify) depends on package C, and the Cheeseshop’s dependency rule is wrong, and it causes the wrong version of package C to be downloaded and installed, and the version number it should be is visually similar to the one it installed (say, 2.3.1 vs. 2.4.1), and it quickly scrolls up your terminal window, and package C version 2.4.1 is in fact incompatible with package D, and you’re tired, you can waste a lot of time chasing your tail.
Seek Nuance 