After talking to mjacob, I now understand why the pypy-c tests were failing so badly.

Re the pypy/python2 errors: It looks like there might be some bug in pytest. If you try running this command:

pypy pytest.py  pypy/module/_hashlib/ pypy/module/faulthandler/

It should fail with the same error seen in the python2 pastebin above.

I now understand that the buildbot must not run these two tests in the same test execution, explaining why the behavior I'm seeing is different.

Given all this, I think I now understand this correctly. Thanks again to mjacob for explaining!