Revert "Remove importlib-metadata and importlib-resources"

This reverts commit 38435ae81c.

lib/importlib_resources/tests/test_contents.py

@@ -0,0 +1,43 @@
+import unittest
+import importlib_resources as resources
+
+from . import data01
+from . import util
+
+
+class ContentsTests:
+    expected = {
+        '__init__.py',
+        'binary.file',
+        'subdirectory',
+        'utf-16.file',
+        'utf-8.file',
+    }
+
+    def test_contents(self):
+        contents = {path.name for path in resources.files(self.data).iterdir()}
+        assert self.expected <= contents
+
+
+class ContentsDiskTests(ContentsTests, unittest.TestCase):
+    def setUp(self):
+        self.data = data01
+
+
+class ContentsZipTests(ContentsTests, util.ZipSetup, unittest.TestCase):
+    pass
+
+
+class ContentsNamespaceTests(ContentsTests, unittest.TestCase):
+    expected = {
+        # no __init__ because of namespace design
+        # no subdirectory as incidental difference in fixture
+        'binary.file',
+        'utf-16.file',
+        'utf-8.file',
+    }
+
+    def setUp(self):
+        from . import namespacedata01
+
+        self.data = namespacedata01