Modify directory cleanup to avoid ResourceWarning

Deleting the variable does trigger the clean up of the temporary
directory but it also issues a warning:

ResourceWarning: Implicitly cleaning up <TemporaryDirectory '/var/folders/1x/h9lknjv97cx6lw9npp95xkyr0000gn/T/tmpav1qw4d_'>

Replace the tearDown with an explicit cleanup() call. Also ensure
that any errors in clean up do not cause the tests to fail.

tests/test_calibrateImage.py

@@ -310,7 +310,7 @@ def setUp(self):
         detector = 42
 
         # Create a and populate a test butler for runQuantum tests.
-        self.repo_path = tempfile.TemporaryDirectory()
+        self.repo_path = tempfile.TemporaryDirectory(ignore_cleanup_errors=True)
         self.repo = butlerTests.makeTestRepo(self.repo_path.name)
 
         # dataIds for fake data
@@ -366,7 +366,7 @@ def setUp(self):
         self.butler.put(afwTable.SimpleCatalog(), "ps1_pv3_3pi_20170110", self.htm_id)
 
     def tearDown(self):
-        del self.repo_path  # this removes the temporary directory
+        self.repo_path.cleanup()
 
     def test_runQuantum(self):
         task = CalibrateImageTask()