test: add hypothesis

Allow python3 tests to use the new hypothesis testing.

I am targeting python 3 for additional testing of existing code.
Don't spend the additional time on Travis CI (where python2 is tested)
where I have to ask for more time on the platform.

New code should be testable on both platforms. If we have a need to
test with hypothesis on python 2 for new code, we can revisit this.

.github/workflows/ci-test.yml

@@ -119,7 +119,7 @@ jobs:
       # note pytest-env is not needed for redis password as there is
       # no password on CI's redis.
       - name: Install pytest and other packages needed for running tests
-        run: pip install flake8 mock pytest pytest-cov requests sphinx-tabs
+        run: pip install flake8 hypothesis mock pytest pytest-cov requests sphinx-tabs
 
       - name: run flake8 - abort for syntax error, otherwise warn only
         run: |