Try to remove cr.commit (and rollback) from module and db install:
* put a savepoint around test data loading
* remove a bunch of commits sprinkled throughout
* remove rollback on data loading failure (assuming it bubbles up, the
entire module's installation should be rolled back)
* add commit right before the tests are run, so they can run isolated
and still see whatever was done when installing their module
* convert a few explicit closing to context managers
Xavier Morel
93c0d7e811