New sphinx version 3.0.0 breaks docs

[shukon]

New sphinx version breaks building of docs... https://www.sphinx-doc.org/en/master/changes.html#release-3-0-0-released-apr-06-2020

Fixed for now by enforcing sphinx version 2.4.4

[shukon]

While this is not a critical bug by any means, it is annoying. To elaborate a little, reproduce:

$ pip install --upgrade matplotlib pillow sphinx sphinx-gallery sphinx_rtd_theme
$ cd docs
$ make buildapi
$ make html
sphinx-build -b html -d build/doctrees   . build/html
Running Sphinx v3.1.0
loading pickled environment... done
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 0 source files that are out of date
updating environment: 0 added, 34 changed, 0 removed
Reading sources... [ 73%] apidoc/cave.cavefacade  

and there it freezes. Varies for the percentage, but always cave.cavefacade or cave.utils.timing. On investigation, the line from functools import wraps is responsible. Commenting it out in both files results in successfully building docs.