nbsphinx 0.8.0

https://pypi.org/project/nbsphinx/0.8.0/

• Don't overwrite Pygments background in notebook code cells.
  To get rid of those ugly greenish code blocks, remove pygments_style = 'sphinx' from your conf.py.
• Switch documentation to
  insipid <https://insipid-sphinx-theme.readthedocs.io/>_ theme by default
• Require Python 3.6+