Originally reported by: Jason R. Coombs (BitBucket: jaraco, GitHub: jaraco)

In our tests, we have this fixture:

@pytest.fixture
def EMEA_options():
    options_stream = pkg_resources.resource_stream(__name__,
        'EMEA exporter options.yaml')
    return yaml.load(options_stream)['exporter_options']

Beginning with pytest 2.4.1 (maybe 2.4), we started seeing this error when the fixture runs:

NotImplementedError: Can't perform this operation for loaders without 'get_data()

That error occurs in pkg_resources (part of setuptools 1.1.6) because the NullProvider is selected instead of the EggProvider (the package is installed using 'develop').

With pytest 2.3.5, the EggProvider is elected.

The apparent reason is that in pytest 2.4, the __loader__ of the package in question is:

(Pdb) __loader__
<_pytest.assertion.rewrite.AssertionRewritingHook object at 0x482e850>

So it seems the __loader__ is being wrapped in an AssertionRewritingHook, which causes pkg_resources to identify it incorrectly, and thus not use the EggProvider.

I'm hoping this regression is an unintentional oversight and easily corrected. Please let me know if I can provide more detail to help resolve the issue.

• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/366