Fix unit test regressions from the warning assertions change.
Review Request #10800 — Created Nov. 18, 2019 and submitted
A change to
assert_warns()was made on the release-4.0.x branch, which
was then backported to release-3.0.x. This was designed to improve
warning support, allowing testing against multiple warnings. However, it
also required that the checks be more specific, comparing warning
classes directly instead of checking subclasses, and comparing messages
directly instead of making them optional. This regressed a few tests on
release-3.0.x, which did not exist on release-4.0.x.
This change updates those tests to follow the new, stricter testing
Unit tests pass.