AssertionRewritingHook object has no attribute find_spec

[jaraco]

Beginning with pytest 3.0.1, the tests in setuptools (example build) are failing with this error:

AttributeError: 'AssertionRewritingHook' object has no attribute 'find_spec'

This issue was not revealed with pytest 3.0.0 due to the issue with collection.

For now, setuptools is pinning to pytest 2.x (see pypa/setuptools#765) to work around the issue.

I expect this issue may be triggered by the (admittedly hacky) sandboxing that setuptools does, so setuptools may have some culpability. I have not researched the error further, so I welcome advice on what might be triggering this error.