Mark the file as xfail for now.

It's more important to be able to include the important resources than to exclude unwanted ones. Ref #4475.

setuptools/tests/test_setuptools.py

@@ -301,6 +301,7 @@ def test_findall_missing_symlink(tmpdir, can_symlink):
         assert found == []
 
 
+@pytest.mark.xfail(reason="slated for removal; excluding tests is hard #4475")
 def test_its_own_wheel_does_not_contain_tests(setuptools_wheel):
     with ZipFile(setuptools_wheel) as zipfile:
         contents = [f.replace(os.sep, '/') for f in zipfile.namelist()]