Check reStructuredText syntax along with flake8

[jparise]

This verifies the integrity of the setup metadata so we can be even more
confident in our PyPI releases.

[sigmavirus24]

Shouldn't this be twine check at this point? I thought setup.py check --restructuredtext was deprecated.

[jparise]

Shouldn't this be twine check at this point? I thought setup.py check --restructuredtext was deprecated.

Ah, perhaps it is. I see twine check was introduced in version 1.12.0 (September 2018), and I was still using 1.11.0 locally.

[jparise]

twine check appear to only be useful for checking the integrity of a distribution file. It's not good for continuous linting, unless we add a build step which always generates a distribution candidate.