Problem

When trying to start psychopy on Arch Linux and error is thrown because the matplotlib dependency on the certifi package is not installed. This is not surprising since certifi is listed in the requires.txt file in the matplotlib egg-info and the Arch package of matplotlib does not include certifi as a requirement. While certifi appears to be a requirement in setup.py, the installation guide (https://matplotlib.org/users/installing.html#dependencies) does not list it as a dependency

Suggested Improvement

If certifi is truly a dependency, it should be listed in the documentation