Improve our internal coverage tests

[tybug]

Our ./build.sh check-coverage job has a misconfiguration where it only checks that hypothesis.internal.conjecture is fully covered:

hypothesis/hypothesis-python/tox.ini

Line 204 in 259813a

--cov=hypothesis.internal.conjecture --cov-config=.coveragerc \

This should be --cov=hypothesis, to ensure we have coverage over the entire codebase.

And it turns out we don't! We should add coverage tests to get to 100% coverage here, then fix the --cov argument.

[jobh]

It looks like the problem is of recent date, b688f39.

It's best to fix it quickly so the coverage gap doesn't grow too overwhelming. I can probably make a start over the weekend.

Good catch @tybug!

[tybug]

I can’t take too much credit, this was discovered independently at pycon 😄. Glad to hear this isn't years old, at least.

[jobh]

Reopened to track the three remaining coverage holes

• hypothesis/core.py:1109
• hypothesis/internal/entropy.py:130
• hypothesis/stateful.py:391