Pytest: 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.

[jaraco]

@nicoddemus It seems that pytest 3.0.3 re-introduces the failure fixed in 3.0.2. As you can see above, I've pinned Setuptools to 3.0.2 to allow the tests to continue to pass. I haven't had time yet to investigate. I think I should re-open this issue, although if you think it's better to open a new one, feel free to do that or suggest the same.

[nicoddemus]

Fixed as discussed in pypa/setuptools#810.

[astrojuanlu]

I am observing this issue again, but I can't reproduce it locally...

https://circleci.com/gh/poliastro/poliastro/4018

[astrojuanlu]

For the record, pinning to <4.6 fixed the issue.

[blueyed]

The real error is:

E TypeError: cannot unpack non-iterable NoneType object

See https://github.com/pytest-dev/pytest/issues/5358.

[licht1stein]

Is it possible that the issue is triggered by test classes with > 20 tests?

[nicoddemus]

Is it possible that the issue is triggered by test classes with > 20 tests?

Yes, but can you please post the full output so we can check if it is the same problem?

[licht1stein]

Is it possible that the issue is triggered by test classes with > 20 tests?

Yes, but can you please post the full output so we can check if it is the same problem?

Here it is below. Fixed by using pytest < 4.6

==================================== ERRORS ====================================
_________________ ERROR collecting test/models/test_country.py _________________
<frozen importlib._bootstrap>:900: in _find_spec
    ???
E   AttributeError: 'AssertionRewritingHook' object has no attribute 'find_spec'

During handling of the above exception, another exception occurred:
.venv/lib/python3.7/site-packages/py/_path/local.py:701: in pyimport
    __import__(modname)
<frozen importlib._bootstrap>:983: in _find_and_load
    ???
<frozen importlib._bootstrap>:963: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:902: in _find_spec
    ???
<frozen importlib._bootstrap>:876: in _find_spec_legacy
    ???
.venv/lib/python3.7/site-packages/_pytest/assertion/rewrite.py:169: in find_module
    source_stat, co = _rewrite_test(self.config, fn_pypath)
.venv/lib/python3.7/site-packages/_pytest/assertion/rewrite.py:404: in _rewrite_test
    rewrite_asserts(tree, fn, config)
.venv/lib/python3.7/site-packages/_pytest/assertion/rewrite.py:453: in rewrite_asserts
    AssertionRewriter(module_path, config).run(mod)
.venv/lib/python3.7/site-packages/_pytest/assertion/rewrite.py:701: in run
    new.extend(self.visit(child))
/usr/local/lib/python3.7/ast.py:262: in visit
    return visitor(node)
.venv/lib/python3.7/site-packages/_pytest/assertion/rewrite.py:828: in visit_Assert
    top_condition, explanation = self.visit(assert_.test)
E   TypeError: cannot unpack non-iterable NoneType object

[nicoddemus]

Yes, this will be fixed in 4.6.1, should be released soon.

[curlup]

what should I do if i see this on 4.6.3 ?

[nicoddemus]

Hey @curlup,

what should I do if i see this on 4.6.3 ?

Probably report it as a bug, preferably with a small reproducible example.