Fix resource leaks from get_dataset_from_uri

Author: dhirving

tests/test_simpleButler.py

@@ -942,13 +942,15 @@ def test_dataset_uris(self):
                     f"ivo://org.rubinobs/usdac/lsst-dp1?repo={label}&id={ref.id}",
                 ):
                     result = Butler.get_dataset_from_uri(dataset_uri)
+                    self.enterContext(result.butler)
                     self.assertEqual(result.dataset, ref)
                     # The returned butler needs to have the datastore mocked.
                     DatastoreMock.apply(result.butler)
                     dataset_id, _ = result.butler.get(result.dataset)
                     self.assertEqual(dataset_id, ref.id)
 
                     factory_result = Butler.get_dataset_from_uri(dataset_uri, factory=factory)
+                    self.enterContext(factory_result.butler)
                     self.assertEqual(factory_result.dataset, ref)
                     # The returned butler needs to have the datastore mocked.
                     DatastoreMock.apply(factory_result.butler)
@@ -958,6 +960,7 @@ def test_dataset_uris(self):
                 # Non existent dataset.
                 missing_id = str(ref.id).replace("2", "3")
                 result = Butler.get_dataset_from_uri(f"butler://{label}/{missing_id}")
+                self.enterContext(result.butler)
                 self.assertIsNone(result.dataset)
 
         # Test some failure modes.