Code review comment for lp://qastaging/~ted/snapcraft/ros-catkin-plugin

So I think the complexity is taken care off and the other little comments.

I'm going to leave the *attr() ones because they match the other code, if we're going to change those I'm happy with that, but it should be one branch to change them all.

Wait for Sergio's comment/discussion on the config variable and how we want to handle that.