The private API used here was removed in pytest 5.
There is a public API now, pytest.ExitCode.TESTS_FAILED,
however that is not yet available in pytest 4.
We hardcode the value 1 instead, it is unlikely to be changed.
Once pytest 4 is gone, we can switch to the new API.
See https://github.com/pytest-dev/pytest/issues/5125
Historically, we ignored the test results as we don't have the
manpower to investigate the failures on various architectures.
Since most of the test pass, I've added a 1% failure tolerance
on everything except x86_64, so we do no longer need to ignore the
results. This makes it easier to spat that it's no longer a couple
test that fails on some random architecture but rather a more
severe problem.
In the process I had to disable test_decomp on ppc64le, because it
segfaults.
