I met such a situation when I had already used system package manager like aptitude or pacman to install that very package, or dependency package
(they, pip and system package manager, do not know each other, while they install package at the same folder, some site-package thing, so it's easy to get a file already exist like problem)
You need to see which is conflict, open your python console, try to import it, and see where is it with module_name.file, remove it(or the folder) manually (please backup before problem really solved).
Or just use pip and system package manager to verify which has been already installed
