Fix test state leakages causing failures if subvertpy isn't installed.
Review Request #12154 — Created March 15, 2022 and submitted
The SVN unit tests change the test backend in
setUp(), and restore the
old state in
tearDown(). Or, they're supposed to. If a backend isn't
installed (such as
subvertpyon Python 3.8+), we raise a
This actually bypasses
tearDown(), meaning we keep the old test
This eventually impacts other tests that depend on a working SVN
We now handle the management of the backend in
tearDownClass(), which won't be affected by the
reduces the work that needs to be done per-test, and ensures we'll end
up with the original state once the tests have completed.
All unit tests pass without