This was introduced in rBAcadeb9991cb6.
Here’s a suggested fix.

I don’t understand what you are trying to do, Alexander's branch is for 2.8 as implied in the branch name, right?

I can’t test on Mac OS, but it works for me on Linux when applied upon the latest commit.

In T52758#621084, @Ivan Cappiello (icappiello) wrote:

I believe the correct behaviour should be a sort of install external module button (just like the install addon button) that will copy the external module in the correct syspath making the module local and available. Doing this will require also a list of installed modules and a remove module button in the preference.

I don't think it was retained as a priority but I mentioned it at the meeting we had after the conferences. Not during my talk, though.

Hi guys, happy new year.
We met during the Blender conference, I'm the cutout guy.

Thanks, my bad.