WIP: Get rid of assert reinterpretation in rpython tests
Assert reinterpretation has long been deprecated in pytest and was removed in version 3.0. This branch allows rpython tests to run with assert rewriting by adding
rpython.rlib.objectmodel.assert_(), which behaves like an RPython
assert statement but doesn't get rewritten by pytest.
Fixing the test suite is then just a matter of mechanically replacing all asserts in RPython functions defined in test files by this new