Responded to reviewer.

Wrapped the output of DIAObjectCollection.get_object_ids as a list.

python/lsst/ap/association/association.py

@@ -86,6 +86,7 @@ def run(self, dia_sources, exposure):
             Input exposure metadata containing the bounding box for this
             exposure.
         """
+        # Assure we have a Box2D and can use the getCenter method.
         bbox = afwGeom.Box2D(exposure.getBBox())
         wcs = exposure.getWcs()
         ctr_coord = wcs.pixelToSky(bbox.getCenter())

python/lsst/ap/association/dia_collection.py

@@ -109,7 +109,7 @@ def get_dia_object_ids(self):
         ------
         A list of ints
         """
-        return self._id_to_index.keys()
+        return list(self._id_to_index.keys())
 
     def update_dia_objects(self, force=False):
         """ Update the summary statistics of all DIAObjects in this

tests/test_dia_collection.py

@@ -171,7 +171,7 @@ def test_score_and_match(self):
                 0.1 * src_idx,
                 -1)
         score_struct = obj_collection.score(
-            src_cat, afwGeom.Angle(1.0, units=afwGeom.arcseconds))
+            src_cat, 1.0 * afwGeom.arcseconds)
 
         self.assertFalse(np.isfinite(score_struct.scores[-1]))
         for src_idx in range(4):
@@ -217,7 +217,7 @@ def test_empty_dia_collection(self):
         for src_idx in range(5):
             # Our scores should be extremely close to 0 but not exactly so due
             # to machine noise.
-            self.assertFalse(np.isfinite(score_struct.scores[src_idx]))
+            self.assertTrue(np.isinf(score_struct.scores[src_idx]))
 
         updated_indices = dia_collection.match(src_cat, score_struct)
         self.assertEqual(len(updated_indices), 5)