fontbakery update mechanism is not working (regardless of using MacOS or GNU+Linux)

[felipesanches]

On MacOS I was prompted to update fontbakery because 0.7.34 is available and the ZIP release downloaded from this repo currently contains 0.7.31.

When I accepted the update, it failed and told me something went wrong.

---

I tried the same on GNU+Linux and initially it did not ask for an update (because I had the latest fontbakery installed via pip in the same virtualenv). So I manually downgraded to 0.7.31 by running:
pip install fontbakery==0.7.31

and then when I reopened FB UI, I was prompted to update.

By accepting, I got a failure message on the terminal:
ERROR: Can not perform a '--user' install. User site-packages are not visible in this virtualenv.

but got a "SUCCESS" message on the dialog. Subsequent execution of FB UI prompted me again for an update, which is evidence that the update actually did not work.