Documentation build fails

[malmans2]

The documentation build fails. I think the problem is that readthedocs is not compatible with the latest version of sphinx. Someone already opened an issue, so let's keep an eye on it. If the readthedocs team fixes it, we'll just have to trigger a new build. Otherwise, we'll probably have do downgrade sphinx.

Here is the link to the open issue:
readthedocs/readthedocs.org#6870

[malmans2]

Fixed!