TL;DR: for some reason ros installs opencv rather differently, so I had to build 3.1 from source to get the shared library files where they needed to be.
Interesting. When building the samples I ran into the same issue, and decided to look around for my opencv 3.1 installation. According to python I had it installed, particularly through ros when calling cv2.file, however when going there I managed to find only one file related to opencv. Maybe I wasn't looking hard enough but I could not find the rest of the files. I decided to just give up, install opencv 3.1 using their instructions from source, and voila, everything wen't fine.