[2.7.1] Test Errors with Python 3.9

[olebole]

Hi,

on Debian, we are currently migrating to Python 3.9. With the released version, we get now errors when running the tests:

============================= test session starts ==============================
platform linux -- Python 3.9.0+, pytest-4.6.11, py-1.9.0, pluggy-0.13.0
rootdir: /tmp/autopkgtest-lxc.dhe2dv4q/downtmp/autopkgtest_tmp
plugins: openfiles-0.5.0, arraydiff-0.3, hypothesis-5.41.2, remotedata-0.3.2,
asdf-2.7.1, astropy-header-0.1.2, doctestplus-0.7.0, filter-subpackage-0.1.1,
cov-2.8.1
collected 462 items / 2 errors / 460 selected

==================================== ERRORS ====================================
_______________ ERROR collecting tags/core/tests/test_ndarray.py _______________
/usr/lib/python3/dist-packages/asdf/tags/core/tests/test_ndarray.py:25: in <module>
    TEST_DATA_PATH = helpers.get_test_data_path('', module=test_data)
/usr/lib/python3/dist-packages/asdf/tests/helpers.py:68: in get_test_data_path
    with resources.path(module, name) as path:
/usr/lib/python3.9/contextlib.py:117: in __enter__
    return next(self.gen)
/usr/lib/python3.9/importlib/resources.py:175: in _path_from_reader
    opener_reader = reader.open_resource(norm_resource)
<frozen importlib._bootstrap_external>:995: in open_resource
    ???
E   IsADirectoryError: [Errno 21] Is a directory:
'/usr/lib/python3/dist-packages/asdf/tags/core/tests/data'
_____________________ ERROR collecting tests/test_types.py _____________________
/usr/lib/python3/dist-packages/asdf/tests/test_types.py:20: in <module>
    TEST_DATA_PATH = str(helpers.get_test_data_path(''))
/usr/lib/python3/dist-packages/asdf/tests/helpers.py:68: in get_test_data_path
    with resources.path(module, name) as path:
/usr/lib/python3.9/contextlib.py:117: in __enter__
    return next(self.gen)
/usr/lib/python3.9/importlib/resources.py:175: in _path_from_reader
    opener_reader = reader.open_resource(norm_resource)
<frozen importlib._bootstrap_external>:995: in open_resource
    ???
E   IsADirectoryError: [Errno 21] Is a directory:
'/usr/lib/python3/dist-packages/asdf/tests/data'
!!!!!!!!!!!!!!!!!!! Interrupted: 2 errors during collection !!!!!!!!!!!!!!!!!!!!
=========================== 2 error in 1.59 seconds ============================

This was reported as bug Debian#975529. With Python 3.8, the tests run fine. Do you have a patch available that fixes this? Or do you plan a new version soon?

[eslavich]

I ran our test suite on a Travis linux container with Python 3.9 and didn't see any failures. Here's the result when running the tests out of the repo clone:

https://travis-ci.com/github/asdf-format/asdf/jobs/446366394

and from the installed package with pytest --pyargs asdf:

https://travis-ci.com/github/asdf-format/asdf/jobs/446366410

I don't know why Debian behaves differently, but looking at the documentation for importlib.resources.path it seems clear that we're misusing it by asking for a directory.

[jdavies-st]

I suspect that helpers.get_test_data_path should just be removed. Or just return a path instead of returning the opened file in a with context manager.

[eslavich]

Resolved by #889